New and little‐known species of Didemnidae (Ascidiacea, Tunicata) from Australia (Part 3)

The majority of the 58 species discussed, including 10 new species, were collected by scuba divers at 5–10 m in waters around Australia. Species are from Leptoclinides (11), Polysyncraton (11), Didemnum (19), Trididemnum (7), Lissoclinum (8), Clitella (1), and Diplosoma (1), and new species are in all except Trididemnum and Diplosoma. Additional characters (including a pyloric vesicle reported previously in the Holozoidae and several unrelated didemnid taxa) have been detected for the monotypic genus Clitella Kott, 2001, which is recorded for only the second time. A review of known Australian ascidian species confirms the Didemnidae as the most speciose ascidian family in these waters. In this family, there appears not to be appreciable gene flow between tropical and temperate waters and few species have a continuous tropical–temperate range. A preponderance of Western Pacific non‐indigenous species is in the north, while indigenous species, some probably isolated from related tropical ones, are dominant in the temperate waters of the southern half of the continent. Although intraspecific variation and convergence obscures species differences, some aspects of the living organisms detected in in situ photographs contribute to identification. Keys to Australian didemnid species described since the publication of the Australian Ascidiacea part 4, Didemnidae (Kott 2001) are included.


Introduction
All taxa of the Ascidiacea are firmly fixed to or rooted in, respectively, hard or soft substrata and are not readily collected by dredge or bottom sampler. Therefore, until scuba equipment (generally from late in the 1970s) made the (often cryptic) habitats of these organisms accessible to collectors, they were well sampled only in accessible intertidal and shallow sub-tidal depths. Sampling of the family Didemnidae was especially subject to these restraints and at least partly for this reason, the study of this family was neglected until the last decades of the 20th century. The number of ascidian species known to occur in Australian waters increased from little more than 100 in the early 1950s to over 700 in recent studies (Kott 1985(Kott , 1990a(Kott , 1990b(Kott , 1992a(Kott , 1992b(Kott , 2001(Kott , 2002a(Kott , 2002b(Kott , 2002c(Kott , 2003(Kott , 2004a(Kott , 2004b(Kott , 2004c and in the present work: see Tables I and II). Nevertheless, it is clear that these organisms, and especially the Didemnidae, are still not well known, and many locations and habitats have yet to be explored, a further 10 species being described in the present study. Davis et al. (1999), in a study emphasizing the poor state of knowledge of Australian marine invertebrates, found that of 535 known species of the Ascidiacea, 24% of large solitary and 40% of the ''more obscure colonial ascidians'' were known from less than five records. Only relatively few species of the Didemnidae were included in their study, the family being relatively neglected at that time. It was revised several years later by Kott (2001) and is well represented in recent collections; especially those made by scuba, as many of the species are conspicuous, having large and brightly coloured colonies. Determination of the structure of both colonies and zooids of species in this family is, nevertheless, difficult and often intractable. As Kott (2001) indicated, despite improvements in accessibility to, and the quality of, light and electron scanning microscopy, determination of the morphology of these complex colonies and small zooids and the identification of species and resolution of their relationships are confounded by intraspecific variations in the colonies (e.g. colour, shape, distribution of spicules and form of the common cloacal cavities) that occur with growth, population variation, habitat and fixation; and by the fact that the relatively few definitive and/or readily determined characters (e.g. length and origin of the retractor muscle, form and length of the siphons, body shape and dimensions) in the small, simplified and often immature zooids are often altered by contraction, which also obscures other characters (e.g. numbers and shape of stigmata and vas deferens coils). As well, because of their habitual cushion or sheet-like form, colonies in this family suffer more mutilation than most other taxa when removed from the hard or rubble substrate to which the whole undersurface is attached. Fortunately, most species of the family contain the characteristic calcareous spicules that are not affected by growth or environmental factors and, in a neutral medium, are not affected by fixatives or preservatives. Although interpretation of scanning electron micrographs of these spicules sometimes is subjective, their maximum size and shape (including the length, shape and number of rays) often provide the only relatively reliable, stable and readily determined genetically controlled characters available for species determination. Their relevance to phylogeny at genus level, however, is limited.
General biogeographical trends noted for other internally, as well as externally, fertilized taxa of the Ascidiacea (Kott 1985) are emphasized in the Didemnidae, which is the most species-rich ascidian family in Australian waters. However, fewer didemnid species have a continuous tropical-temperate range than other families, the temperate fauna is largely endemic and the majority of species occurring in the tropical northern part of the continent range widely through the Indo-West Pacific (see Tables I-III). Continuing studies of the Australian Didemnidae are adding to the evidence of the Indo-West Pacific nature of the northern Australian ascidian fauna and are revealing new taxa, intraspecific variations (both genetic and environmentally induced), new growth patterns and extensions to the known geographic ranges of these organisms.
Australia by Loisette Marsh, Shirley SlackSmith and others from the Western Australian Museum. The relative status of synonyms is indicated by '','' (senior) or ''.'' (junior) before the species name.

Remarks
Although the lobes on the surface of the colony often are cylindrical as in some species of the genus Atriolum, the present species does not have the long atrial siphon opening directly into a central cavity as in the latter genus. The species appears to be a southern Australian one, at present known only from Kangaroo I., characterized by its relatively small spicules with few rays which have chisel-shaped and conical tips. The spicules are gathered into small clumps in the surface layer of test where they are mixed with equal-sized clumps of black pigment. Spicules are also in a sparse layer lining the large common cloacal spaces. In life, the colonies look the same as they do in preservative and the in situ photographs, and the newly recorded colony and type material are similar. The appearance of these colonies is distinctive. Leptoclinides compactus has bulky colonies with rounded lobes with terminal common cloacal apertures, similar spicules (but with more rays) and although the spicules have a similar distribution as in the present species, they form a continuous layer beneath the superficial bladder cell layer rather than being gathered into small clumps.

Description
Smooth-surfaced colonies, with an extensive posterior abdominal cavity, encrusting weed. Although a variety of colours have been recorded for the living colonies (see Kott 2001), the newly recorded one from Darwin (QM G 308728) is pink with white markings identical with specimens from the southern and central Great Barrier Reef (Kott 2001, Plate 2G, H). The newly recorded colony from Cockburn Sound is soft and translucent, growing around debris (mud, worm tubes) which is embedded in the central test core and has sparse spicules in the surface test. In the other specimens the usual layer of small crowded spicules is at the surface. A single and less crowded layer is always on the base of the colony and spicules are sparse elsewhere. They are burr-like, to 0.03 mm diameter and diverse, having rod-like, fusiform or slate-pencil urchin or club-shaped rays previously described. Except when spicules are sparse in the superficial layer of test, a single layer is in the test lining the urn-shaped branchial siphon and they outline the margins of the stellate branchial apertures. Branchial siphons are constricted at the base where there is a false siphon. Fourteen stigmata are in the anterior row on one side of the branchial sac. The gut forms a double loop in the specimens from Shark Bay and Cockburn Sound, which have about 14 male follicles in the grape-like three-dimensional mass. Specimens from Port Hedland are immature, and as well as lacking gonads, the gut forms a straight vertical loop rather than the double loop characteristic of the mature specimens of this species.

Remarks
This species is readily characterized by its small, diverse spicules in a thin layer at the surface and on the base of the colony, the false siphon at the base of the branchial siphon, the double gut loop, the grape-like mass of testis follicles and the S-shaped course of the vas deferens. Usually this species has spicules crowded in the surface of the test, and their restricted distribution in the colony from Cockburn Sound could have resulted from its location at the southern extremity of the species' geographic range. The zooid has the usual species characters. Its urn-shaped branchial siphon, recorded previously for L. durus Kott, 2001, is a common characteristic of the dubius species group (see Kott 2001

Description
The colony is a small, thin irregular cushion, in life a pale yellow colour with opaque rims of crowded spicules around the large sessile common cloacal apertures randomly distributed over the surface. Branchial apertures, containing a plug of white spicules, are slightly depressed into the surface. Spicules are mixed with bladder cells in the superficial layer of test and are present, but not crowded through the remainder of the colony, being absent only from the base. Spicules are stellate, to 0.06 mm diameter, with 9-11 rays with chiselshaped or conical pointed tips and a ray length/diameter ratio of 0.24. The common cloacal cavity is a horizontal space at oesophageal level. Zooids have a moderately long, funnel-shaped branchial siphon. Atrial siphons are short, opening directly into the oesophageal common cloacal cavity. The oesophageal neck is relatively long and the abdomen is bent up at right angles to the longitudinal axis of the thorax. Stigmata are obscured by contraction and the number was not determined. Gonads are not present.

Remarks
Owing to contraction and the absence of gonads in this specimen, its identification is based on the shape and size of the spicules, the form of the colony and the configuration of the common cloacal systems. Leptoclinides placidus Kott, 2001 from central Queensland has similar spicules throughout the colony, including their presence in the superficial bladder cell layer, but a more extensive three-dimensional common cloacal cavity with posterior abdominal spaces.

Description
The newly recorded colony is a fleshy slab with a more or less even surface raised into rounded elevations about 0.5 cm apart, each with a terminal common cloacal aperture. A thin superficial layer of bladder cells mixed with spicules is on the upper surface and spicules are evenly distributed through the remainder of the colony although they become sparser toward the base. In the newly recorded specimen spicules are to 0.07 mm and have 9-11 pointed or chisel-shaped rays in optical transverse section. Three clumps of spicules are in each siphon lining. Zooids are tightly enclosed in test and are difficult to remove from it. The branchial siphon is funnel-shaped and the atrial aperture short, cylindrical and posteriorly orientated. The gut loop is bent up into a double loop. Gonads were not detected.

Description
The newly recorded colony is a complex three-dimensional mass, with parts of it overgrowing its surface. Spicules are in a thin layer in the surface test but are sparse elsewhere. An extensive, horizontal, posterior-abdominal common cloacal cavity is beneath the crowded zooids lying parallel to one another at the surface of the colony. Spicules have long, pointed fusiform or conical pointed rays and there are some very rare globular spicules. The branchial siphon is cylindrical with six small points around it and a false siphon at its base. The posteriorly orientated atrial siphon has five pointed papillae around the rim of the aperture. Fourteen stigmata are in the anterior row of the branchial sac. The gut loop is folded up into a double loop. Gonads are immature in the newly recorded specimen.

Remarks
The species was previously recorded from Shark Bay by the German Expedition to SW Australia (see Michaelsen 1930). Initially, Michaelsen (1930) distinguished the present species from the related L. dubius by the form of the colony. Subsequently, Kott (2001) found differences in the spicules, those of L. dubius being more diverse than the spicules of the present species which mostly have pointed fusiform or long conical pointed rays although a few are small and globular spicules which Hartmeyer (1919) had also detected. The present species is more often recorded off north-western Australia than north-eastern Australia while the reverse is true of L. dubius. However, neither species is restricted to either one of these locations. This is one of the few tropical species not yet recorded outside Australian waters. Hastings, 1931 ( Figures 1C, 18D) Leptoclinides lissus Hastings 1931, p 93 and synonymy.

Description
The newly recorded colony is a firm, irregular sheet with grey patches in the surface where black pigment particles are mixed with the crowded white spicules in the thin surface layer of test. The surface of the colony is hard and a superficial spicule-free layer of bladder cells is not present. Spicules are present throughout, but are most crowded in the surface and on the base of the colony. They are stellate, to 0.56 mm diameter, with 9-11 conical or chisel-shaped ray tips. Primary common cloacal canals extend almost the whole length of the zooids and penetrate around the relatively large thoraces of individual zooids. The vas deferens coils seven times around the four or five testis follicles. Many embryos, including tailed larvae, are in the basal half of the colony. The larval trunk, 0.64 mm long, has three pairs of ectodermal ampullae, three antero-median adhesive organs and a short external horizontal ectodermal ampulla on the left side. The tail is wound three-quarters of the way around the trunk.

Remarks
Other than the holotype, the newly recorded specimen is the only one known and the larva is described for the first time. The species differs from most in the genus in its extensive thoracic common cloacal systems and its crowded spicules. The shape of the spicules and the number of rays is similar to L. aciculus Kott, 2001, L. constellatus Kott, 2001 and L. placidus Kott, 2001 (which all have larger spicules), L. compactus Kott, 2001 (which has a particularly extensive three-dimensional cloacal system and spicules confined to thin layers in surface and base and around the common cloacal cavity), and L. rigidus Kott, 2001 (which has a superficial layer of bladder cells).

Description
The holotype is a fragment of a white sheet with an even surface covered with minute, crowded, spicule-filled, flat-topped papillae. Stellate branchial apertures are surrounded by crowded spicules. Spicules are crowded throughout the surface layer of test and are in a thin layer on the base of the colony, but they are sparse elsewhere. Spicules are small (to 0.04 mm diameter), burr-shaped to stellate, with 17 or more conical pointed to roundtipped rays in optical transverse section.
Zooids are very small. The atrial aperture is posterior, almost sessile and two-lipped. Strong transverse muscles are in the interstigmatal bars, fine parallel thoracic muscles are in the pallial thoracic wall and a circular lateral organ is in the outer body wall on each side of the base of the short atrial siphon (opposite the interspace between the third and last rows of stigmata). Twelve stigmata are in the anterior row of the branchial sac and two coils of the vas deferens surround a circle of five to seven club-shaped male follicles. A large egg is outside the outer coil of the vas deferens.

Remarks
Despite their small size, these zooids are characteristic of the genus Leptoclinides. The few vas deferens coils is reminiscent of the dubius group, but the present species has a regular circle of testis follicles rather than the grape-like cluster in the dubius group of species (Kott  In preservative, the colony is a robust, brown slab. The surface has a regular quilt-like pattern of bolster-like elevations, which comprise about one-quarter of the total thickness of the colony and are separated from each other by deep narrow depressions. Occasional large, soft, funnel-like common cloacal apertures about 1-2 cm apart are on the surface between the surface elevations. A thick spicule-free superficial bladder cell layer containing brown pigment cells covers the surface elevations. Similar brown pigment cells surround the zooids, lying free in the space between the test and the body wall of the zooids. Spicules are in a layer beneath the superficial bladder cell layer, but are completely absent from the translucent basal half of the colony. A thin layer of test forming the roof of the deep common cloacal canals is at the base of each of the surface depressions and the branchial openings of the zooids are along each side of the base of these depressions. The common cloacal canals are deep, extending at least the full length of the zooids (about three-quarters of the depth of the colony). Spicules are of moderate size with five to seven long, narrow pointed arms in optical transverse section. The ray length/spicule diameter ratio is about 0.5. Zooids are robust but contracted and this together with the scattered brown pigment cells that surround them and the spicules in the surrounding test obscure them and the number of stigmata in the branchial sac. The posterior atrial siphons, each with five minute pointed lobes around the aperture, open into each side of the top of the common cloacal canals. Abdomina are large with a relatively voluminous gut sometimes forming a vertical loop and sometimes with the post-pyloric part bent at right angles to the longitudinal axis of the zooid. Five coils of the vas deferens surround about five or six large testis follicles.

Remarks
Both the colonies (with the regular quilted pattern, the deep depressions over the common cloacal canals that interrupt the spicule layer, the thick superficial layer of bladder cells) and the spicules with their long, narrow arms are unusual in this genus. Both colonies and spicules differ from those of L. constellatus Kott, 2001, L. exiguus Kott, 2001, and L. rigidus Kott, 2001, the colonies of the present species having a larger and more regular quilted pattern and a thicker superficial layer of bladder cells, and the spicules having fewer, longer and thinner and invariably pointed rays (rather than sometimes having the chisel-shaped rays of the other species).

Description
The newly recorded colonies are tough irregular sheets with a smooth surface. A thin superficial bladder cell layer is interrupted by the branchial siphons and their plugs of spicules in the siphon linings. The test is translucent, the spicules being only moderately crowded in the upper part of the colony. They also line the common cloacal cavities but are sparse in the base and up to the basal one-third of the total thickness of the colony. The primary common cloacal canals are deep and some extend into posterior abdominal cavities. Owing to the not very crowded spicules, preserved colonies appear to have a grey network where the deep primary canal interrupts the thickness of the spicules through the depth of colony. This results in the thin layer of surface test over the common cloacal canals being translucent and grey. However, in situ photographs show the living colonies to be blue, sometimes with some brown flecks. Spicules are characteristically stellate, to 0.08 mm diameter with 9-11 pointed to chisel-tipped conical rays in optical transverse section.
Zooids have a simple vertical gut loop, five coils of the vas deferens and four to eight testis follicles.
Larvae, with a trunk 0.75 mm long, are recorded for the first time in colonies collected from Darwin (QM G308708). They have three lateral ectodermal ampullae on each side of the three antero-median adhesive organs and a lateral horizontal ampulla on the left side of the trunk.

Remarks
The tough colonies, stellate spicules, common cloacal canals and the absence of spicules from the basal part of the colony are characteristic of this species. The blue colour of the living colonies also may be characteristic and distinguishes the species from L. constellatus Kott, 2001 and L. pulvinus sp. nov., which also have a quilted surface but are brown and beige. The temperate species L. seminudus Kott, 2001 also has a quilted surface and similar spicules, but lacks a posterior abdominal cloacal cavity and has a larval trunk only 0.4 mm long (see below). Leptoclinides exiguus Kott, 2001 has spicules with more numerous rays. Kott, 2001 ( Figure 18F) Leptoclinides seminudus Kott 2001, p 82;2004a, p 736.

Description
In preservative, the surface of the tough, newly recorded colony has a mosaic of grey scalelike elevations separated by brownish grey depressions. Generally, the test is cartilaginous and translucent rather than opaque and brittle. Black pigment is mixed with spicules in the superficial bladder cell layer over the depressions and is crowded into randomly distributed patches on the remainder of the surface. Spicules are mixed with the bladder cells in the superficial layer of test and are present around the zooids, but are sparse in the basal half of the colony. They are stellate, to 0.068 mm diameter with 9-11 rays with conical or chiselshaped tips in optical transverse section. Zooids are along each side of the deep primary common cloacal cavities that surround the pillars of solid test beneath the surface elevations. In life, the test over the common cloacal canals is blue, forming a blue network around the white zooid-free surface elevations of the surface.

Remarks
The present species is distinguished from the tropical L. rigidus by the absence of a posterior abdominal extension of the common cloacal cavity and the larvae which are reported to have a trunk only 0.04 mm long.

Description
The newly recorded colony is relatively thick. Zooids are seen as yellow points along each side of the canals that surround irregular to elongate zooid-free areas. Common cloacal apertures are randomly distributed sessile apertures on the top of slight surface elevations. The primary common cloacal canals extend the full depth of the zooids and sometimes extend into oesophageal and occasionally posterior abdominal canals. Spicules are evenly distributed throughout and never crowded. There is no superficial aspiculate layer of test.

Remarks
Colonies, spicules and zooids are as previously described.

Description
The newly recorded colonies, spicules, zooids, and larvae are as previously described. The specimen differs from others in the distribution of spicules which do not form an opaque layer at the surface, although the branchial lobes, like six-petalled daisies, protrude from the surface of the colony, one petal usually being larger than the others. Also, spicules are present in the basal and the central test mass with some mud and other debris. Clumps of zooids are suspended in the extensive common cloacal cavity in test ligaments connecting the surface with the basal or central test. Larvae are found to have particularly large external horizontal ampullae on the left side and this has been confirmed in larvae previously recorded.

Remarks
The surface of the colony, with the spicule-filled lobes protruding from the surface, resembles the surface of some colonies of Didemnum cygnuus Kott, 2001 and Polysyncraton papyrus Kott, 2001 (see below). The common cloacal cavities are better developed in the newly recorded colony than has been reported previously. The appearance of the living colony, including its greenish colour, is identical with that shown by Kott (2001, Plate 5B) as is the colony from South Shell I., Darwin (QM G308604: Kott 2004b). Kott (2004b) is wrong in referring to the larval external horizontal ampulla on the right side of the larval trunk (it is always on the left); and the specimen from which the larva was taken is QM G308616 (not QM G308608 sic).

Description
The colony is a small (2 cm maximum diameter), relatively soft cushion with spicules crowded throughout, absent only from a superficial layer of bladder cells through which the short branchial siphons project, the branchial apertures being conspicuous on the surface of the colony. A large sessile common cloacal aperture with a spicule-free rim is in the centre of the upper surface. The common cloacal cavity is thoracic. Spicules are relatively small (to 0.046 mm), globular burr-shaped with numerous crowded rod-like rays. Small pointed branchial lobes are on the rim of the branchial apertures, the atrial aperture has a biramous anterior lip and there is a retractor muscle projecting from halfway down the short oesophageal neck. Gonads were not detected.

Remarks
The newly recorded specimen confirms the southern Australian range for this species, which previously was known only from two widely separated records. Although the largest spicules have a slightly greater diameter than has previously been recorded for the species, they are the same burr-like globular shape and the small cushion-like colonies with a central common cloacal cavity are similar to those of the syntypes from Rottnest I.

Description
In preservative, the newly recorded colony from Tasmania is a flat, smooth encrusting sheet. Small inconspicuous common cloacal apertures are slits or four or five lobed openings with slightly protruding frilled lips. Branchial apertures are tightly closed and inconspicuous. However photographed in situ the surface of the colony is raised into evenly spaced, contiguous, uniform rounded lobes, each 5-7 mm diameter with a terminal common cloacal aperture. The specimen from South Australia is less contracted and in the in situ photograph its surface lobes are not so high. It has stellate branchial apertures lined with spicules. The preservative is stained yellow. In life, colonies are salmon-pink to a crushed strawberry colour. Each of the surface swellings contains a single common cloacal system, the zooids opening on the sides of the swellings or lobes around the central or terminal common cloacal aperture. The common cloacal cavity is shallow and horizontal at thorax level. Spicules are crowded tightly throughout the colony and the surface is raspy. They are stellate, to 0.07 mm diameter with seven to nine and occasionally five relatively short, robust, conical rays. In one of the specimens (SAM E3261) the spicules are to 0.07 mm diameter but in the other the largest spicules are only 0.05 mm diameter. Small stellate spicules to 0.02 mm diameter are present but are never as numerous as the larger ones.
Zooids have a narcissus-shaped branchial aperture, constricted at the base and with six pointed lobes around the opening. About eight stigmata are in the anterior row of the branchial sac. Zooids are in vegetative phase with oesophageal buds, and gonads were not detected. Short vascular stolons with terminal ampullae project from the ventral side of the double gut loop. A robust, tailed larva, the trunk 0.72 mm long, is in one colony (SAM E3250). It has 16 crowded lateral ampullae along each side of the three antero-median adhesive organs which have thick, swollen stalks. The tail is wound almost the whole way around the trunk. The cerebral vesicle contains a relatively large ocellus and otolith. A large, vertical, oval yolk mass is halfway along the trunk and a long horizontal external ampulla projects posteriorly from the base of the circle of lateral ampullae on the left side of the trunk.

Remarks
The in situ photographs of the newly recorded specimens and of the type specimens are very alike. Although the species was characterized partly by the numerous small spicules in some parts of the test, this is inconsistent and it is possible that the proportion of smaller spicules is affected by the part of the colony from which the sample came. Kott (2004b) observed the systems with zooids arranged around the common cloacal aperture, but did not specify their isolation from one another. Nevertheless, she did observe that they resembled the common cloacal systems in P. glaucum Kott, 2001, which does have independent systems (albeit larger spicules to 0.09 mm diameter with 9-11 pointed rays in optical transverse section). Also similar to the present species are P. multiforme Kott, 2001 with spicules to 0.05 mm diameter and 17-19 pointed to blunt-tipped rays in optical transverse section, P. pavimentum Monniot, 1993 with large spicules to 0.1 mm diameter and 13-15 pointed to truncated rays in optical transverse section as well as some globular spicules, and the New Zealand species P. lithostrotum (Brewin, 1956) with almost globular spicules to 0.08 mm diameter, short, blunt spicule rays and different larvae. Polysyncraton pavimentum: Kott, 2002a ,P. polysystema sp. nov. with large spicules to 0.08 mm diameter and 9-11 conical and truncated ray tips should be added to the list of similar species (see below, P. polysystema sp. nov.). The colony of the present species also differs from that of the related species listed above in that each independent system is contained in a lobe that projects from the surface of the colony rather than being a flat system level with the colony surface.

Description
The newly recorded colony is a thin encrusting sheet with spicules crowded in the surface, and present, although not crowded, through the remainder of the colony. Spicule-filled papillae are on the ventral side of each branchial aperture. The extensive common cloacal cavity is at thorax level. Although the preserved specimen is mutilated and squashed, the form of the systems is evident in the in situ photograph showing white-rimmed common cloacal apertures evenly distributed over the surface of the colony in the centre of green areas dotted with white, spicule-filled branchial apertures. White spicule-filled ridges surround these green circular to polygonal areas that each represent a single common cloacal system.

Remarks
Photographs of the newly recorded specimen show it to be identical with the type material (Kott 2001, Plate 5E). The species appears to be related to the group of Polysyncraton spp. which has independent common cloacal systems (see P. galaxum, Remarks, above). The green colour of the present species and its flat systems level with the upper surface help to distinguish it from the red-pink P. galaxum in which each system is contained in a lobe projecting from the upper surface of the colony. Polysyncraton pavimentum Monniot, 1993 and Polysyncraton polysystema sp. nov. (.P. pavimentum: Kott, 2002a), also have flat common cloacal systems but they are pale pink. The latter species also has the same spicule diameter (0.08 mm) and number of rays in optical transverse section (9-11) as the present species. However, its spicule rays are conical with pointed or truncated tips rather than being long and blunt-tipped as they are in the present species.

Description
The newly recorded colony is a hard, brittle, biscuit-like plate with a rounded margin and spicules crowded throughout. The upper layer of test, forming the roof of the horizontal, thoracic common cloacal cavity, is brownish and contains thin, branched pigment cells. The margins of the stellate branchial apertures are outlined in white spicules. Sessile common cloacal apertures are randomly placed on the surface and are surrounded by dark pigment. The thoracic sheaths of the zooids as they cross the common cloacal cavity are white with spicules, as is the basal layer of test in which the abdomina are embedded. The majority of the spicules are stellate (to 0.66 mm diameter) with 11-13 pointed conical rays in optical transverse section. However, there are some with truncated, flat-tipped rays and also there are some globular spicules. Zooids are long and narrow, with a long tulip-shaped branchial siphon and a conspicuous spiculefilled siphonal lining. The atrial aperture has a characteristic slightly spoon-shaped, narrow atrial lip from the upper rim of the opening. Eight stigmata are in the anterior row of the narrow branchial sac. Six coils of the vas deferens surround a number of testis follicles.

Remarks
Despite its wide geographic range, this species is remarkably stable, with little apparent morphological variability. The colonies always are hard and biscuit-shaped, with darkly pigmented surface test and white basal test, the spicules include globular as well as stellate ones, and the characteristic spoon-shaped atrial lip is unique to this species. Although Kott (2001) reported only five coils of the vas deferens, six are shown in her figure (Kott 2001, Figure 54C) and were detected in the newly recorded material.

Description
The newly recorded colonies are small (less than 1 cm) irregular plates on weed. The characteristic blister-like vesicles surround each stellate branchial aperture on the surface of the colony. Spicules also are characteristic, to 0.05 mm diameter, with 9-11 short, crowded, conical to round-tipped rays in optical transverse section. The zooids are immature.

Remarks
Although these colonies are immature, the circle of vesicles around each branchial aperture and the spicules with their short, crowded rays are characteristic of this temperate species, which so far is known from only relatively few records.

Description
The newly recorded specimen consists of fragments of a soft, thin sheet. The surface appears spotted to the naked eye owing to the daisy-like patterns created by the spicules crowded into each of the six lobes of the branchial apertures that project slightly from the upper surface. Spicules are evenly, but rather sparsely distributed in the remainder of the surface test and on the base of the colony. They are not present in other parts of the colony. Spicules are small, to 0.035 mm diameter, and they have 9-11 short conical rays in optical transverse section. In preservative, the pinkish brown zooids can be seen through the surface but in life the colony is a translucent greyish blue colour. Common cloacal apertures protrude from the surface. About seven spicule-filled radial ribs extend from the aperture across the roof of the common cloacal cavity. The thin test over these common cloacal cavities may be elevated in life when the internal pressure is maintained by the ciliary current. The thoracic common cloacal cavity surrounds clumps of thoraces and the abdomina are embedded in the basal test.
Thoraces are relatively large with about 10 narrow, spindle-shaped stigmata per row. Branchial lobes are narrow and pointed. The atrial aperture completely exposes the branchial sac to the common cloacal cavity and an anterior atrial lip is short and bifid. The vas deferens coils five times around four or five testis follicles. A retractor muscle was not detected.

Remarks
The type specimens of P. papyrus have similar spicules but they are more crowded than they are in the newly recorded specimen and the zooids have a retractor muscle. Other characters appear to be similar and confirm Kott's (1954) description of the types and in particular the gonads, with five coils of the vas deferens (see Kott 2001).
The spindle-shaped stigmata have been reported for Leptoclinides brandi and the spicule-filled branchial lobes forming petal-like patterns on the surface have previously been reported for Didemnum cygnuus Kott, 2001 and some specimens of Polysyncraton cuculliferum. Neither of these characters appears to have any phylogenetic significance.

Description
The laterally flattened, fleshy corms narrowing to a thick, fleshy, basal stalk, have four or five large, sessile common cloacal apertures around the narrow edge of the colony, each with a thin transparent rim. These are especially conspicuous along the centre of the top of each lobe but are depressed into the surface in the preserved colony. Zooids are in branching double rows or along each side of circular common cloacal cavities. They have short branchial siphons, long tongue-shaped or bifid atrial lips and a long, narrow retractor muscle. Four coils of the vas deferens surround the seven or eight testis follicles.

Remarks
The present species is distinguished from Polysyncraton rica, with which it has been confused, by its stalked aspiculate colony and the position of the sessile common cloacal apertures (which in P. rica are single terminal openings on the top of conical surface elevations). Despite Kott's (2004b) report of three loose coils of the vas deferens, four are readily detected in a recent revision of zooids from previously recorded as well as the newly recorded colonies described above.

Remarks
Although their colonies are similar and their spicules are the same size, P. pavimentum: Kott, 2002a andP. pavimentum Monniot, 1993 from Chesterfield Reef and New Caledonia appear not to be conspecific. The nominal species has 13-15 pointed rays in optical transverse section, while those of the new species have only 9-11 conical, pointed or truncated rays in optical transverse section.
Polysyncraton lithostrotum: Monniot, 1993 andP. pavimentum Monniot, 1993, both from Chesterfield Reef and New Caledonia, have similar stellate spicules with 13-15 pointed rays in optical transverse section and some globular spicules, six coils of the vas deferens, a small retractor muscle, similar larvae with the larval trunk 0.7-0.8 mm long, and a circle of 24 larval epidermal ampullae. However, Kott (2001) was wrong in thinking them synonymous, for, despite their very similar appearance, the maximum diameter of spicules of P. lithostrotum: Monniot, 1993 is only 0.04 mm-half the size of the largest spicules in P. pavimentum Monniot, 1993. Further, the New Zealand species, P. lithostrotum (Brewin, 1956) is distinguished from the tropical P. lithostrotum: Monniot 1993 by its larger spicules with rounded rays. It is probable that P. lithostrotum: Monniot 1993 is another undescribed species in this related group, with a maximum spicule diameter of 0.04 mm and pointed spicule rays-different from the large spicules with rounded rays of the New Zealand species.
It appears that the scale line of 0.1 mm applied to the larvae of P. lithostrotum: Monniot, 1993 is incorrect, the larval trunk being reported as 0.8 mm long but measuring 1.6 mm (Monniot 1993, Figure 1F).

Description
Both newly recorded colonies are thick, firm jelly-like and aspiculate. The relatively small zooids with large bifid anterior atrial lips line the deep, circular common cloacal canals that surround the zooid-free stands of solid test. In living specimens some brown pigment is in the surface test over these canals and around the common cloacal apertures at their junctions. In preservative, these canals are made conspicuous by the faecal pellets in them, although small brown pigment particles can be detected in the surface test.

Remarks
Many other species in this and other genera have similar cloacal systems with the zooids lining the circular canals that surround each zooid-free stand of solid test. However, most of these species have spicules throughout the test, or at least in a layer at the surface. The present species sometimes has a layer of spicules at the surface but usually it is patchy and the spicules are smaller than those in P. arvum Kott, 2004c and larger than those of P. dromide Kott, 2001, the two other tropical species of this genus with zooids along each side of circular common cloacal canals (see Remarks, P. arvum Kott, 2004c).

Remarks
The newly recorded colony resembles those previously described in its soft, fleshy consistency, smooth surface with a superficial layer of bladder cells and lobes or in this case with part of the surface overgrowing and partly fusing with the other half. Spicules are evenly distributed throughout but are not crowded, and some are characteristically bilaterally (rather than radially) symmetrical with rays on one side longer than those on the other. Zooids, crowded in a layer at the surface, have a robust rectangular thorax with a conspicuous, strong, tapering retractor muscle and three coils of the vas deferens around a circle of four or five testis follicles. The species is unusual in this genus in having only a small atrial tongue. The species has not been recorded outside South Australian waters.
Specimen QM GH2387 from Flinders I., erroneously assigned to P. pedunculatum, has been re-examined and found to belong to the present species. Although the in situ photograph of the living colony (Kott 2001, Plate 6D) is dramatically different from the deck photograph (Kott 2001, Plate 6G), the preserved colonies are identical.

Description
The newly recorded colony is a thin irregular encrusting sheet. The under surface is hard, spicule-filled with some fine, sharply defined parallel ridges crossing it. Spicules are crowded throughout the remainder of the colony, including the smooth upper surface where they obscure the branchial apertures. Spicules mostly are stellate, to 0.06 mm diameter, with 13-15 short crowded rays in optical transverse section, although some have shorter, round-tipped rays and are almost globular. Sometimes the branchial siphon is about half the length of the remainder of the small thoraces in the newly recorded colony, which appear to be juveniles. Only six stigmata per side reducing to four in the posterior row were detected in the newly recorded colony, although Kott (2001) recorded eight in the anterior rows of the small zooids she examined. The abdomina are mature, each with a well-developed, undivided testis surrounded by 10 coils of the vas deferens.

Remarks
The hard, ridged, basal test of this species occurs also in Leptoclinides durus Kott, 2001 and Polysyncraton millepore Vasseur, 1969 (see above), L. uniorbis F. and C. Monniot, 1996 from Micronesia, andDidemnum parancium Kott, 2001 from Townsville. The present species is distinguished from these and others by its spicules and the large number of vas deferens coils, both of which are clearly recognizable in all the specimens so far examined. There are 12 separate records of this species from the Capricorn Group at the southern end of the Great Barrier Reef. Since it is recorded also from NW Australia and the Indian Ocean it can be expected to occur in coral reef locations in the Indian and western Pacific Oceans.

Description
The surface of the colony is divided into opaque scale-like elevations separated from one another by narrow circular depressions. In preservative, the test over these depressed areas is relatively thin and is slightly translucent and beige colour, while the elevated areas they enclose, which surmount solid pillars of test, are white with crowded spicules. The spicules are stellate, to 0.07 mm diameter, with 9-11 conical, sometimes blunt-tipped rays in optical transverse section. The circular common cloacal canals vary in depth, sometimes extending the depth of the thoraces, but sometimes the whole depth of the zooids. Thoraces are small, with a fine retractor muscle from halfway down the oesophageal neck. Large sessile atrial apertures lack an atrial tongue. The branchial lobes are triangular and pointed and the siphon is contracted but conspicuous and may be long in more relaxed zooids. Large yellow eggs are in the abdomen (which is embedded in the basal test) but testes were not detected.

Remarks
The zooid-free scale-like elevations on the upper surface, like those in D. grande Herdman, 1886 andD. microthoracicum Kott, 2001, are larger and a different colour from those of D. poecilomorpha F. and C. Monniot, 1996 and D. leopardus sp. nov. The species is distinguished from others by its relatively large spicules with 9-11 robust conical rays crowded throughout the colony and by the form of the common cloacal systems and the quilted colony surface.

Description
In preservative, the colony is a circular grey slab, the colour resulting from black faecal pellets mixed with white spicules. A few sessile common cloacal apertures are on the surface and occasionally these seem to be extended into large openings extending along one of the common cloacal canals. This is apparent only and results from the absence of spicules or other test inclusions in the thin roof of the common cloacal canal. Spicules are evenly distributed in the surface and on the base of the colony and in the lining of the deep primary and posterior abdominal common cloacal cavities. They are large, to 0.1 mm diameter and have seven to nine robust pointed rays in optical transverse section. Thoraces are clumped together and are surrounded by the primary common cloacal cavities but the abdomina are embedded in the basal test. Sometimes the primary common cloacal cavities penetrate the clump of thoraces, separating them from one another in independent spicule-filled test sheaths. Some debris is embedded in the basal test. In life, colonies are white cushions with large common cloacal apertures around the margin. Zooids are small with a fine tapering retractor muscle. The atrial opening is wide but lacks any atrial lip. Four or five vascular stolons project into the test from the concave ventral aspect of the gut loop. The colony is in vegetative phase, with oesophageal buds. Gonads were not detected.

Remarks
The species is distinguished by its large spicules with relatively few rays in optical transverse section and their absence from some parts of the colony. Didemnum microthoracicum Kott, 2001 has similar spicules but they are crowded throughout the colony rather than being confined to certain layers as they are in the present species; and it has a quilted pattern on the colony surface. Kott, 2001 ( Figures 15G, 19H) Didemnum cygnuus Kott 2001, p 169;2004c, p 40.

Description
The newly recorded colony is a thin film of test, greenish grey in life, with sparse but evenly distributed spicules, growing over and around pebbles and incorporating them into the test. Spicules are stellate, to 0.05 mm diameter, with five to seven sturdy conical rays in optical transverse section. Zooids are small, with a short retractor muscle and five coils of the vas deferens.

Remarks
The thin colonies and their small, sturdy, stellate spicules with few conical rays, some of which are particularly thick, are characteristic of this species, which previously was known only from Western Australia.

Description
The newly recorded colony is a thin, encrusting sheet with burr-like spicules to 0.05 mm diameter crowded throughout. In life, the specimen is a greenish grey with a mosaic of small yellow flecks in the surface. In preservative, the colony is grey with a white margin around the colony. Although they occupy the whole depth of the colony, the zooids are small with no more than six stigmata per row, a rounded atrial lip and dark cells in the haemocoel. The grey colour of the colony results from the dark zooids seen through the white spicules in the surface layer of test.

Remarks
The species is similar to D. albopunctatum Sluiter, 1909 andD. parancium Kott, 2001, both of which have crowded burr-shaped spicules in thin colonies. However, in the present species the spicules are larger. Further, the zooids of D. parancium are larger than the present species and they have characteristic large transparent vesicles in the haemocoel that have not been detected in D. fragile.

Description
One newly recorded colony (SAM E3239) is sessile and divided into two lobes with a smooth and even surface. The other is a solid stalked lobe, the test of the stalk harder than that of the head and its surface is transversely wrinkled with a particularly crowded layer of spicules in the surface, which is raspy. Spicules are tightly packed in the surface of the colony but are less crowded internally where the test is softer, gelatinous and translucent. Spicules are stellate, up to 0.09 mm diameter, but they have a large size range. They have 9-13 short, robust conical rays in optical transverse section. The spicule rays are not especially crowded at the base. Common cloacal cavities are relatively shallow thoracic or oesophageal spaces but they become more extensive toward the top of the heads and extend into some posterior abdominal cavities near the base of the heads. Some spherical masses of minute dark brown globular bodies are in the test amongst and behind the zooids. Orange pigment cells are scattered in the test and in the body wall of the zooids. An in situ photograph of the newly recorded stalked specimen (SAM E3266) is of a conspicuous, bright red and white mottled lobe with two large distended terminal common cloacal apertures.
In the preserved specimen, branchial apertures are seen as small whitish points on the surface rather than stellate openings, but that could be the result of contraction. The small zooids have a relatively long branchial siphon, sessile, transverse atrial openings, a short retractor muscle from halfway down the oesophageal neck and the gut forming a double loop. Large yellow eggs are present and the vas deferens coils 11 times around the testis.

Remarks
The species is characterized by the robust, lobed colonies, and the large spicules with numerous short conical rays crowded in the surface of the colony lobes. The species is known only from temperate waters. Sluiter, 1909 ( Figure

Description
One of the newly recorded colonies (QM G308730) is rather irregular, with the surface raised into rounded lobes with two or three large sessile common cloacal apertures with white crowded spicules in the rim of each opening. The living specimens are whitish beige. In preservative, black spherical bodies lie free in the spaces around the zooids (rather than being embedded in the test) and the brown-black colour of the zooids dominates the colonies. Thoraces are small with a long retractor muscle from halfway down the oesophageal neck. The spicules have the characteristic club-shaped spicule rays crowded through the colony as previously described for this species. Brown larvae are present in specimens collected in July.

Remarks
Although all characters are as previously described, including the larvae, the newly recorded colony is whitish beige rather than the range of colours that Kott (2001) reported for the living specimens.

Remarks
Although this specimen appears to have been dried out, the zooids can still be seen to line the primary cloacal canals that surround the zooid-free areas and the characteristic spicules to 0.1 mm, with 9-11 strongly pointed conical rays in optical transverse section present throughout the colony. The newly recorded specimen is the most southerly record for this well-characterized tropical species on the western Australian coast.

Description
The newly recorded specimens are parts of sheet-like encrusting colonies, crowded throughout with small (to 0.04 mm diameter) stellate spicules with five to nine conical and pointed rays in optical transverse section. In places, the surface of the colony has minute upright spicule-filled papillae between the stellate branchial openings which are outlined in spicules. Groups of thoraces have their ventral borders embedded in stands of test that connect the basal part of the colony to the surface test. Each clump of thoraces is surrounded by a deep common cloacal canal which sometimes penetrates between the thoraces separating them from one another, each in an independent sheath of test. Abdomina are embedded in the basal test. Zooids are small with a small comma-shaped thorax crossing the horizontal common cloacal cavity and the abdomina are embedded in the basal test. Six stigmata are in the anterior row of the branchial sac, the oesophageal neck is long and a retractor muscle extends from about halfway down the oesophageal neck. The gut forms a double loop. Nine coils of the vas deferens surround the undivided testis. Small larvae, the trunk 0.5 mm long, have four pairs of long finger-like ampullae each side of the three anteromedian adhesive organs and the tail is wound three-quarters of the way around it.

Remarks
The species is readily identified by its hard, sheet-like colonies, small zooids with small pointed branchial lobes and double gut loop, retractor muscle from halfway down the oesophageal neck, and especially by the small stellate spicules which have five to nine relatively long, pointed conical rays in optical transverse section and are never more than 0.04 mm diameter. The colony sometimes has a three-dimensional growth-form (see Kott 2001). Didemnum vestum Kott, 2000d from the Atlantic coast of North America has a three-dimensional growth form similar to some of the colonies of the present species. However, it has smaller spicules with significantly shorter rays, eight coils of the vas deferens and a larger larva with six pairs of ectodermal ampullae. Didemnum vexillum Kott, 2002b from New Zealand (which has erroneously been regarded as conspecific with the northern Atlantic species) has a similar growth form but is readily distinguished from both D. incanum and D. vestum by its larger spicules with more rays (see Kott 2004d).
Both Didemnum mantile Kott, 2001 andD. domesticum Kott, 2004c have similar small spicules with seven to nine long rays in optical transverse section, but, respectively, six and seven coils of the vas deferens. Didemnum madeleinae F. and C. Monniot, 2001 has larger spicules (to 0.05 mm diameter) with only five to seven conical spicule rays in optical transverse section and seven coils of the vas deferens. Didemnum perlucidum Monniot, 1983 from Guadeloupe has a larva similar to the present species and spicules with five to nine rays in optical section, but they are smaller than the spicules of the present species (to 0.03 mm diameter) and it has a sheet-like colony and only eight coils of the vas deferens. Other specimens assigned to D. perlucidum from the tropical western Pacific and Brazil (see Kott 2004d) are not sufficiently described for confident assignation. Other species, including D. granulatum Tokioka, 1954, have seven to nine rays in optical transverse section but usually their spicule diameter is 0.06 mm or more, readily distinguishing them from the present species.
The Tasmanian record is the most southerly for this temperate species, that appears to be one of the few known trans-Tasman species. Kott, 2001 ( Figures 8B, 20D) Didemnum jucundum Kott 2001, p 197 and synonymy;2004b, p 2495.

Description
The preserved colony is a flexible thin sheet with spicules evenly distributed throughout, but not crowded. The zooids can be seen through the test, conferring a pinkish glow to the colony. The test tears readily and has the consistency of cotton wool. Zooids are readily removed from it. Although spicules to 0.82 mm diameter have been reported previously, the maximum diameter detected in the newly recorded specimen is 0.066 mm. Spicules have 13-15 crowded, conical rays in optical transverse section. Large common cloacal apertures with spicule-free rims are scattered randomly on the surface. Zooids have relatively long cylindrical branchial siphons that make small bumps on the surface of the colony. The atrial apertures are sessile and lack an atrial tongue. They have a particularly strong retractor muscle that is free of the zooid from about halfway down its long oesophageal neck. Gonads were not detected in the newly recorded specimen.

Remarks
The species can be distinguished by its zooids with a long cylindrical branchial aperture, the retractor muscle branching away from the zooid well down the long oesophageal neck and the characteristic spicules with crowded conical rays. It is known only from the southern temperate waters of the continent.

Description
The colony is thin, hard and brittle and about 30 cm in extent. In preservative, it has a network of irregular cream depressions in the surface that separate it into a mosaic of white slightly elevated, zooid-free scale-like areas. In life, the depressions are brown and the scale-like areas are yellow. Spicules are crowded throughout the test. They are to 0.06 mm diameter with seven to nine robust conical rays in optical transverse section. Ventral surfaces of the thoraces are embedded in the solid test surmounted by these scale-like areas and two or three large sessile common cloacal apertures are on the highest points of the colony where the substrate probably raises it higher than the rest of the colony. The zooids are contracted and the details of their structure were not determined. Gonads were not detected.

Remarks
The colonies of this species have a dramatic appearance. Its spicules resemble those of D. madeleinae and D. incanum but are larger with more rays and the colonies are different. Although the in situ photograph indicates that the living specimen resembles those of Didemnum poecilomorpha F. and C. Monniot, 1996(see Kott 2001, it is distinguished by the lack of plant cell symbionts and the presence of only one type of spicule (stellate ones with 11-13 rays in optical transverse section), the globular spicules present with the stellate ones in the latter species not being present. Kott, 2001 Didemnum mantile Kott 2001, p 203.

Description
The newly recorded colony is white, encrusting, with a white lumpy surface. Evenly distributed stellate branchial apertures have spicules lining their margins. Spicules, crowded throughout, are to 0.04 mm diameter and have seven to nine relatively long conical but blunt-tipped rays in optical transverse section. The colony is contracted and details of the zooid morphology are obscure.

Remarks
This temperate species is known only from two previous records from south-eastern Australia and the new record extends its known range across the southern coast to the western end of the Great Australian Bight. Kott (2001) found only five to seven rays in optical transverse section, but a revision of the micrographs has shown the rays to be identical with those of the present specimen, i.e. seven to nine in optical transverse section. The small spicules with long rays resemble those of the tropical D. domesticum Kott, 2004c, which has a more robust colony with a smooth surface. The type specimens of the present species have a quilted surface resulting from depressions over the common cloacal canals that surround groups of zooids. This quilting is not evident in the newly recorded specimen. However, larvae of D. mantile, though at present not known, may be found to distinguish these species from one another. Didemnum microthoracicum also has spicules with seven to nine rays but they are larger than in the present species, being to 0.09 mm diameter.

Description
The newly recorded colony is a thin encrusting sheet with a quilted surface caused by the surface depression over common cloacal canals that surround zooid-free pillars of solid test. Zooids line the canals. In life, blue pigment is in the surface test over the common cloacal canals. Large sessile common cloacal apertures with spicule-free transparent rims are at the junctions of some of the canals. Spicules are crowded throughout the colony beneath a thin superficial layer of bladder cells. They are relatively large (to 0.09 mm diameter), stellate with seven to nine robust conical pointed rays in optical transverse section. The thoraces are small with no more than six stigmata per row. Gonads were not detected.

Remarks
The relatively large spicules of this species and its circular common cloacal canals around surface elevations of zooid-free test distinguish it from other Didemnum spp. with small zooids and crowded stellate spicules with relatively few rays. Didemnum corium sp. nov. differs in its spicule distribution, the spicules being confined to a layer in the surface, a layer lining the common cloacal cavities and another on the base of the colony; and in the apparent absence of a quilted colony surface.

Description
Newly recorded colonies are of the usual sheet-like encrusting form with crowded spicules of the usual diverse forms, horizontal common cloacal cavities and small zooids with seven coils of the vas deferens. Larvae are present in the colony from Bynoe Harbour collected in May and are described for the first time. The trunk is 0.55 mm long, the tail is wound almost the whole way around it and there are six finger-like lateral ampullae, each with a terminal cap of columnar cells along each side of the three antero-median adhesive organs.

Remarks
This widely occurring tropical species has been recorded only once before from Western Australia; and Cockburn Sound is the most southerly record for it.

Description
The newly recorded, slightly translucent, fleshy colony is encrusting a worm tube. Spicules are present in moderate concentrations in the upper part of the colony and are never crowded. They become sparse toward the base of the colony beneath the shallow, thoracic, common cloacal canals. The spicules are stellate, to 0.05 mm diameter and have 9-11 conical pointed rays in optical transverse section.

Remarks
Despite the general similarity of the spicules to those of D. patulum, they are smaller than has been previously recorded for this species; and this, with the absence of the characteristic circular surface depressions over the common cloacal canals, raises doubts about the species' identity. It is only questionably assigned to D. patulum. Kott, 2001 ( Figure

Description
Delicate, translucent, encrusting colony with spicules largely confined to a sparse but even layer in the surface and another thin layer on the base of the colony. Rare but large, circular, sessile common cloacal apertures are randomly distributed. In life, the newly recorded colony is a pinkish white colour and resembles colonies of Diplosoma translucidum. Deep primary common cloacal canals continue into extensive horizontal posterior abdominal cavities separating the basal test from the zooid-bearing surface layer through which long cylindrical branchial siphons extend to the surface. Spicules are stellate, all with 9-11 conical rays in optical transverse section but they are very variable in size, smaller spicules to 0.03 mm diameter being found in patches and scattered amongst the less common larger ones which are to 0.1 mm diameter. Zooids are characteristically small with a fine retractor muscle, long cylindrical branchial siphon and have a sessile, open atrial aperture without an anterior tongue. In the newly recorded specimen they are in vegetative stage with oesophageal buds and lack gonads.

Remarks
This temperate species is readily distinguished by the two size-groups of stellate spicules and their distribution, the small zooids and the soft colonies with large circular common cloacal apertures. The newly recorded colony appears to be a pinkish white colour that contrasts with the various shades of pink to red previously recorded (see Kott 2001).

Description
Colonies are small (never more than 0.5 cm in maximum dimension). Each branchial opening has a single small pointed papilla associated with it. Spicules are crowded throughout the colony. They are stellate, to 0.06 mm diameter with 9-11 regular conical rays in optical transverse section. Zooids are small, with four rows of only about six stigmata per row and a conspicuous lateral organ with a ventrally facing concavity on each side of the thorax. A robust tapering retractor muscle projects from about halfway down the stout oesophageal neck. Branchial apertures are on short siphons and six sharply pointed lobes are on the rim of the openings. Sessile atrial apertures cross the dorsum of the thorax. Thoraces are covered with conspicuous pointed projecting columnar ectodermal cells (see Kott 2001). Gonads were not detected in the syntype colonies, although tailed larvae are in the basal test. The larval trunk is 0.7 mm long and the tail winds about three-quarters of the way around it. Four pairs of rounded larval ampullae surround the three antero-median adhesive organs.

Remarks
The regularly stellate spicules of these colonies and the larvae lack any unique characteristic that contributes to their identification. Didemnum incanum Herdman, 1899 has similar but smaller spicules. Didemnum granulatum Tokioka, 1954 has larvae that resemble the present species in size and form, and its spicules are not dissimilar, but they have only seven to nine and occasionally only five rays in optical transverse section. The number of spicule rays appears to constitute the principal character separating these species. Further, although spicules up to 0.04 mm diameter often are recorded for D. granulatum (see Kott 2002), some up to 0.06 mm have been recorded (see Kott 2001, Figure 171F) and some of the specimens assigned to this species, especially those with larger spicules, may have been wrongly assigned.

Description
The newly recorded colony is hard, encrusting weed. The surface appears to be a mosaic of slightly elevated, irregular, whitish, zooid-free patches, separated from one another by slight surface depressions (over the common cloacal canals) that appear grey owing to the lack of spicules in the surface test, and the discontinuity in the depth of spicules owing to their interruption by the canals. Zooids are along each side of these canals, their ventral surfaces in the zooid-free stands of test surrounded by the canals. The spicules are characteristically variable in size, the smaller ones mixed with the larger ones (to 0.1 mm). Spicules have 9-11 long, sharply pointed rays in optical transverse section, with the rays sometimes varying slightly in length.

Remarks
The newly recorded material lacks the surface papillae associated with each branchial aperture that is so conspicuous in the type material. Nevertheless, the colony otherwise resembles those previously described. The mixture of small and large spicules appears to be characteristic of this species. It has a wide recorded range in the tropical waters of the Indo-West Pacific. Kott, 2001 ( Figure 16F) Didemnum ternerratum Kott 2001, p 241 and synonymy;2004b, p 2501.

Description
The newly recorded colony is a tough white slab with an even smooth surface. Stellate spicules are crowded throughout. They are to 0.06 mm diameter and have 15-17 short conical rays in optical transverse section. Despite the relatively numerous rays, their bases are not especially crowded together. The common cloacal cavity is a relatively shallow cavity at thoracic level. Zooids are small with about seven stigmata per row in the anterior part of the branchial sac. Gonads were not detected in this specimen.

Description
The newly recorded colony is similar to previously reported specimens (see Kott 2001, Figure 21a, 2004a), being a large, vertical mass with a sessile, terminal common cloacal aperture with a spicule-free rim around the opening. Robust rounded vertical ridges and some projecting branches from the upper part of the colony that fuse with it near the base form prop-like buttresses supporting the vertical colony. A large common cloacal cavity beneath the terminal aperture connects with other cavities that extend down the length of the vertical ridges. The outer zooid-bearing layer of test is connected to a branching central test core by ligaments that cross the cloacal cavities. Spicules are present throughout the test, but are especially crowded in the branching central test core which forms an internal skeletal support for the colony. Spicules are to 0.108 mm diameter and have 9-11 relatively long pointed rays in optical transverse section.
Zooids are small, with black squamous epithelium. The branchial siphon is short and the atrial siphon is posteriorly orientated and trumpet-shaped. A small retractor muscle is at the posterior end of the thorax. A previously recorded specimen (AM Z1681) has been reexamined and, as in the newly recorded specimen, seven coils of the vas deferens were detected, rather than the five coils Kott (2001) erroneously reported.

Remarks
The massive vertical colonies of this species appear to be characteristic. At this stage, smaller colonies have not been assigned to the species and may look quite different. Although the large stellate spicules are not unusual in the species of this genus forming complex three-dimensional colonies, the relatively few vas deferens coils is unusual, T. nobile Kott, 2001 having 10 coils, and T. pigmentatum Kott, 2001, T. sibogae (Hartmeyer, 1910) and T. pseudodiplosoma (Kott, 1962) having eight. Trididemnum lapidosum Kott, 2001 from north-western Australia also has seven coils like the present species. However, although T. lapidosum forms a three-dimensional colony, its colony lobes are flat, its branchial siphon is short and its spicules are to 0.16 mm diameter.
The spicule distribution in the present species appears to be variable. Both the newly recorded colony and the one from Coogee reported on by Kott (2004a) have spicules throughout but they are especially crowded in the central test mass. However, Kott (2001) reported a spicule-free central test mass and spicules in layers at the surface and lining the common cloacal canals. Trididemnum areolatum (Herdman, 1906) ( Figure 16H) Didemnum areolatum Herdman 1906, p 337. Trididemnum areolatum: Kott 2001, p 258 and synonymy.

Description
The newly recorded specimen is a gelatinous, encrusting colony of even thickness. A superficial layer of bladder cells mixed with some black pigment particles and some sparse spicules overlies a single layer of spicules. Spicules also are in a layer lining the common cloacal cavities. The spicules are large (to 0.1 mm diameter) and have 13-15 stubby short conical to rounded rays in optical transverse section.
Zooids have black squamous epithelium and a black endostylar pigment cap. In this specimen the gut is filled with large, muddy faecal pellets that obscure the zooids. Eight coils of the vas deferens surround the undivided testis.

Remarks
Differences from previously recorded specimens were not detected.

Description
The newly recorded colonies are small round cushions to 0.5 cm diameter. Spicules are evenly distributed in the surface test, except around the apertures where they are more crowded. They are less crowded in the remainder of the colony. A common cloacal aperture is in the centre of the upper surface and zooids appear to be in two series inside the outer margin of the colony. Terminal ampullae of vascular stolons are in the basal test around the outside of the colony. Plant cell symbionts are embedded in the test and are not in the common cloacal cavity. Zooids have a short atrial siphon from the posterior third of the dorsal surface.

Remarks
The zooids and colonies are generally smaller but otherwise similar to those previously described. The relatively few records for this species, which has a wide recorded geographical range, are, presumably, a result of its small, inconspicuous colonies.

Description
As previously described, these complex, spongy colonies are large three-dimensional reticula formed by parts of the colony overgrowing the surface and subsequently fusing with it to enclose secondary spaces within the colony. Sometimes weed and other foreign material is incorporated in the test. The common cloacal cavities are three-dimensional with extensive posterior abdominal cavities. Common cloacal apertures are along ridges on the surface and have yellow pigment surrounding them. The spicules are to 1.35 mm diameter, which is larger than previously reported for this species, but they are otherwise identical, having seven to nine sharply pointed conical rays in optical transverse section. They are distributed throughout the colony.
Zooids are small, covered with black squamous epithelium. They have a short retractor muscle from the posterior end of the thorax. Ten tight coils of the vas deferens surround the undivided testis.

Remarks
Spicule distribution in this species is known to be variable, sometimes being present throughout as in the present colony, sometimes being present on the upper surface and in other specimens being sparse or absent altogether (see Kott 2004a). The colony is usually grey in preservative, owing to the black squamous epithelium on the zooids seen through the white spicules and translucent test. This species is distinguished from others by its 10 tight vas deferens coils.

Description
Living colonies have a smooth, even surface, although sometimes lobes overgrow the surface as the colony grows. They have a pearly appearance resulting from the layer of white, crowded spicules beneath a thin superficial layer of bladder cells and minute black pigment particles mixed with the bladder cells. Some yellow pigment is around the common cloacal apertures and also is present internally. Deep primary common cloacal canals extend into posterior abdominal cavities and are lined with a layer of spicules. Spicules are patchy or sparse in the remainder of the colony. Faecal pellets are in the basal test. The large, stellate spicules (to 0.12 mm diameter) have 13-15 long, narrow conical pointed rays in optical transverse section. Zooids are of the usual form with a short posterior atrial siphon and a short robust retractor muscle at the posterior end of the thorax.

Remarks
The colony has a superficial resemblance to the equally smooth-surfaced Leptoclinides brandi, although the latter species has spicules at the surface making it raspy to the touch, and also the species are readily separated by their generic characters. The present species is separated from most other Trididemnum species by its large spicules with numerous finely pointed rays. Although T. savignii has similar spicules, it has eight rather than 10 vas deferens coils.
Some living colonies are reported to have been black (see Kott 2004a), possibly the result of a greater intensity of black pigment in the surface test.

Description
The colonies are robust, and grey, with a translucent test and a fleshy superficial aspicular layer overlying a layer of spicules. Spicules also line the common cloacal cavity. The spicules are large, to 0.11 mm diameter with 11-13 pointed rays in optical transverse section. Faecal pellets are embedded in the basal test.
Zooids are small, with black squamous epithelium on the abdomen and especially on the anterior part of the thorax, although an endostylar pigment cap was not detected. A long retractor muscle projects from the posterior end of the thorax. Eight coils of the vas deferens surround the undivided testis.

Remarks
The species superficially resembles T. areolatum from which it is distinguished by the finely pointed rays of its stellate spicules. The colonies do not form such complex, spongy threedimensional reticula as T. sibogae or T. nobile, both of which also can be separated from the present species by their spicules with fewer rays. The spicules are slightly smaller than, but otherwise similar to, those of T. pigmentatum from which the present species can be distinguished by its thick, fleshy and pigmented superficial layer of test.

Remarks
The species is distinguished from the partly sympatric T. nobile Kott, 2001 by its larger spicules and eight (rather than 10) vas deferens coils.

Description
The syntype colonies are small (to 1 cm maximum dimension) soft cushions with spicules throughout the test. A large horizontal common cloacal cavity (the whole depth of the zooids) containing symbiotic Prochloron cells (0.06-0.07 mm diameter) is in the centre of the colony and a sessile common cloacal aperture is on the upper surface of the colony. Spherical dark cells (0.14 mm diameter) are in the test and cluster around the zooids. The spicules (to 0.034 mm diameter) are globular, burr-like with numerous rod-shaped rays. Zooids cross the common cloacal cavity in independent strands of test. They have two testis follicles and the usual straight vas deferens. Larvae are not present.

Remarks
In the form of the colonies and spicules and the presence of Prochloron symbionts in the common cloacal cavity this species resembles Lissoclinum bistratum (Sluiter, 1909). The present species differs in the presence of dark cells in the colony test, the size of the spicules (significantly smaller than those of L. bistratum) and the presence of two testis follicles (rather than the undivided test of L. bistratum). The species more closely resembles those species of Lissoclinum that have dark test cells around the outside of the zooids and two testis follicles, such as L. badium F. and C. Monniot, 1996, rather than other Lissoclinum symbioses such as L. bistratum and L. timorense (Sluiter, 1909). Previously undescribed, the present species is an addition to the list of didemnid/Prochloron symbioses (see Kott 2001).

Remarks
Colonies of the newly recorded specimen lots from Xmas I. and Western Australia are cushions, with characteristic globular spicules throughout, a single undivided testis follicle and fine Prochloron cells in the common cloacal cavity. Although they concede that the spicules are different and that there are differences in their chemistry, Monniot F and Monniot C (2001) have not been able to separate specimens of L. bistratum from L. voeltzkowi (Michaelsen, 1920), a junior synonym of L. timorense (Sluiter, 1909) and claim that these two species are conspecific. These quite distinct species and their relationships are discussed in detail by Kott (2001). They are not discussed, albeit they are indeed listed, in the catalogue of valid species occurring in Australia (Kott, 1998) where Monniot F and Monniot C (2001) apparently expected the synonymy to be discussed. The two species are well characterized by many aspects of their zooids, larvae and colonies and especially by their spicules (which are dramatically different). It is not possible to assign the specimens newly recorded from the western Pacific by Monniot F and Monniot C (2001) to either of these species as insufficient information is given.

Description
In life, the colony is a thin, delicate, transparent sheet closely adhering to the rubble that it is growing over and that is embedded in the test. Clumps of small zooids are embedded in the test. Spherical larvae with four almost spherical, stalked epidermal ampullae, each with a terminal cap of columnar cells, are along each side of the antero-median adhesive organs, which also have unusually long stalks. A patch of three-dimensional tetrahedral spicules made up of many fine crowded needle-or rod-like rays are in a patch between the ventral flexure of the abdomen and the ventral border of the thorax. The crowded needle-like rays progressively increase in length but simultaneously become fewer along each of the arms to form the terminal points.

Remarks
With the exception of the absence of a complete capsule of spicules around the abdomen, the specimen agrees with previous accounts of the species. It appears that the extent to which this capsule is complete may vary within the species. Similarly, though both the western Pacific Lissoclinum ravarava C. and F. Monniot, 1987(see Kott 2001 and L. limosum Kott, 2001 are known to have a group of spicules between the abdomen and the ventral border of the thorax they are distinct species with significant differences in spicules, colonies, and larvae. Significant differences also exist between L. abdominale: Monniot, 1992 and the nominal species from Guadaloupe, which Monniot (1992) thought were conspecific on the basis of their similar clumps of spicules. The temperate species L. tasmanense Kott, 2001 (distinguished from the tropical species referred to above by the spicule shape and a distinctive larva) also has similar clumps of spicules. There appears not to be any phylogenetic significance attached to these clumps, intraspecific variation in spicule distribution around the abdomen in certain species sometimes resulting in an abdominal capsule of spicules.
That the present species is seldom recorded probably is the result of its inconspicuous appearance and delicacy of the colony.

Description
The newly recorded colonies from South Australia are thin, hard, brittle plates or irregular encrusting colonies with spicules crowded throughout. Stellate branchial openings, their margins lined with spicules, are evenly distributed over the surface and are depressed into it in neat spicule-free circles of test. Circular common cloacal apertures with white, opaque rims are randomly placed on the surface. Spicules are small (to 0.035 mm diameter) and burr-like with 13-15 round-tipped, club-shaped rays in optical transverse section. In life, the colony is pale blue and white. In preservative, dark brown zooids (with brown cells in the haemocoel) can be seen through the common cloacal apertures and through the transparent spicule-free test around the branchial aperture. Clumps of zooids are in the test ligaments crossing the large common cloacal cavity from the surface to the basal test. These subdivide at the surface, separating thoraces from one another. Abdomina are partially or completely embedded in the basal test or are enclosed in the basal part of the test connective. These connecting pillars of test either are rigid with crowded spicules (SAM E3260), or the abdomina, seen through a single layer of spicules around the outside of the test connective, appear to be encased by a capsule of spicules. Zooids have long, narrow thoraces with the large atrial opening exposing almost the whole of the branchial sac (with about six long narrow stigmata per half row) to the common cloacal cavity. Large oval lateral organs are on the body wall on each side of the endostyle. The abdomen is small and bent up underneath the thorax. Gonads were not detected in these specimens.

Remarks
The species is distinguished by its small spicules with relatively few, club-shaped rays. Superficially these colonies, with their blue pigment, depressed branchial apertures and dark haemocoelic cells look like specimens of the tropical species L. reginum Kott, 2001 which, however, has more extensive colonies and larger spicules with more and thinner rays. Lissoclinum levitum Kott, 2001(see Kott 2004a) has different colonies with terminal common cloacal apertures protruding from the surface, and larger spicules with relatively few rays, although the latter are more pointed than the club-shaped rays found in the present species. Lissoclinum ostrearium (Michaelsen, 1930) has a similar colony with the same extensive common cloacal cavity as the present species, however, the spicules shown by Kott (2001, Figure 176E) have more and thinner rays than the present species. Lissoclinum concavum has depressed branchial apertures and similar spicules (although it also has stellate spicules not observed in the present species), its colonies are soft without crowded spicules and a different colour and, even in the absence of the multiple testis follicles that would clearly indicate its identity, the species could not be mistaken for the present one.  newly recorded specimen is from almost the same location as has previously been recorded for this species.

Description
The newly recorded colony is large, hard and sheet-like, with the surface marked off into ridges and prominences, and with common cloacal apertures on the high parts of these prominences. Sometimes branchial apertures can be seen to be in double series each side of surface depressions over the circular common cloacal canals that surround zooid-free areas. The thick spicule-filled surface test is interrupted abruptly by the delicate, spicule-free test around the conspicuous stellate branchial apertures, outlined in spicules, which are depressed into the hard, smooth colony surface. A black dot, where the dark zooid is visible, is in the centre of each branchial aperture. Common cloacal apertures also have black margins where the spicules are absent from the test. The zooids often have their ventral surface supported by the stands of test surrounded by the common cloacal canals, but other zooids cross the common cloacal canal in their own sheath of test. These stands and sheaths of test are always crowded with spicules and are stiff and hard. Common cloacal canals are deep and often the whole zooid or group of zooids is surrounded by the cavity and is connected to the basal test by a stiff, narrow ligament. Spicules are to 0.04 mm diameter, with up to 13 rays in optical transverse section. The majority of the spicules are burr-like to globular with thick flat-tipped rod-like rays, but occasional spicules have long club-shaped rays. Other spicule rays appear to have subdivided, possibly an artefact resulting from their collection and preservation.
Zooids have a large sessile atrial aperture exposing most of the branchial sac directly to the common cloacal cavity. Two male follicles and a straight vas deferens are in the usual position. Large larvae are present in the zooid-free stands of test, just beneath the surface, presumably about to be released. The larvae have six ampullae along each side of the three antero-ventral adhesive organs.

Remarks
The newly recorded specimen does not have the same soft consistency that Kott (2004b) reported for the type material. Also, possibly as a result of a breakdown in the spicules, there is a greater range in the number of spicule rays than Kott (2004b) recorded for the type material. However, the depressed branchial apertures (albeit they occur in other species of this genus) together with the thick spicule rays, almost globular spicules and the occasional spicules with long, club-shaped rays distinguish this species from other Lissoclinum spp. So far it has been recorded only from a restricted part of the southern Australian coast.

Description
The newly recorded colony is soft with large, sessile common cloacal canals. Branchial apertures appear to be depressed into the surface, although this is not conspicuous because the colony is so soft. The test contains morula bodies that make the test cloudy. Spicules are evenly but sparsely distributed throughout. Zooids are in clumps of six to eight clustered around a short, thin test connective anchoring them to the basal test. Abdomina are in these test connectives and are not in the basal test.
The thorax has up to 10 stigmata in each half row. The straight vas deferens extends anteriorly from the centre of a rosette of eight male follicles.

Remarks
The newly recorded colony extends the known range of this temperate Australian representative of the aureum group of Lissoclinum spp. (see Kott 2001), characterized by its numerous testis follicles rather than one or two. Spicules of the newly recorded specimen are sparser than previously recorded for this species, in which their occurrence is known to be variable. In the related tropical species, L. multifidum, abdomina are embedded in the basal test rather than being slung across the common cloacal cavity in a test connective between surface and basal test.

Description
The newly recorded colony is an extensive, hard sheet with spicules crowded throughout. The upper surface of the preserved specimen is even but rough, with some low concentric ridges around the apertures and some long, low corrugations between them. Large, sessile common cloacal apertures are randomly distributed on the surface. The branchial apertures are small openings in the spicule-filled test that sometimes look more like slits than circular or stellate openings. The spicules are small (to 0.035 mm diameter) and burrlike with flat-tipped rod-like rays or almost globular with rounded rays or stellate with conical tips in a basal shaft.
Thoraces cross the shallow, horizontal common cloacal cavity in separate test sheaths and abdomina are embedded in the basal test. Zooids are a brownish colour but there are no separate large pigmented cells around them. Ten stigmata are in the anterior row on one side of the branchial sac. The gut loop is vertical and there are two testis follicles and a straight vas deferens.
Zooids are robust with wide dorsal pharyngeal muscles, numerous longitudinal muscles in the pallial thoracic wall, conspicuous transverse muscles in the interstigmatal bars and a strong retractor muscle which, in these contracted zooids, is short, thick and pointed. Four rows of up to 14 stigmata are in the branchial sac. The gut loop is long and also is robust. Oesophageal buds are forming from the long oesophageal neck. The stomach is large and almost spherical and there is a wide duodenal region. An oval posterior stomach narrows at each end, proximally where it joins the wide duodenum and distally where it enters the proximal part of the rectum (or mid-intestine), which is separated from the distal part by a distinct rectal valve. The distal part of the rectum (or true rectum) is a translucent brownish colour and has a cuticle-like consistency that is different from the remainder of the gut. A large teardrop-shaped vesicle is in the loop of the gut, fitting snugly in the space between the stomach and the gut just distal to the rectal valve, and sometimes it curves over the gut. An opening into the tapered side of this vesicle from the stomach was not detected, although it possibly does exist; and branches or tubules from the vesicle were not detected surrounding this part of the gut. Nevertheless, it is possible that it is a reservoir of the gastro-intestinal (pyloric) gland. Gonads are in the gut loop. The large spherical testis is undivided and the thick vas deferens issues from its postero-lateral aspect and extends anteriorly in a straight line over its outer surface. Yellow eggs are in the basal test.

Remarks
In most genera of the Didemnidae the gut is divided into oesophagus, stomach, duodenum, posterior stomach, and rectum. In Polysyncraton, Lissoclinum, and the present genus, the proximal part of the rectum appears to be differentiated into a distinct additional chamber or mid-intestine which, in Lissoclinum and the present genus, is separated from the distal part of the rectum by a conspicuous rectal valve. This rectal valve is in a similar position to the circle of tubules of the gastro-intestinal gland in other genera (see Polysyncraton: Kott, 2001). The robust zooids, their strong thoracic musculature (unlike the relatively delicate retractor and pharyngeal muscles in Lissoclinum) and the conspicuous differentiation of the gut, the unique larval adhesive apparatus (see Kott 2001), and the turgid thick gelatinous test filled with large bladder cells distinguish this genus from Lissoclinum. Polysyncraton has numerous male follicles and a narrow tubular distal part of the rectum (rather than a firm capacious chamber) that distinguish it from the present genus. The large thorax of the present genus resembles that of some Diplosoma spp. such as D. velatum and D. translucidum but the genera are distinguished by the strong muscles, conspicuous rectal valve, large rectal chamber, and unique larval adhesive equipment (see Kott 2001).
Although the pyloric (or gastro-intestinal) gland occurs throughout the Ascidiacea (see Goodbody 1974), a vesicle similar to the one detected in the present genus was formerly known only in several genera (Distaplia, Hypsistozoa, Neodistoma, and a few species in Sycozoa: see Kott 1990a) of the Holozoidae and in two species of the Didemnidae, namely Didemnum lahillei Hartmeyer, 1909 and Diplosoma gelatinosum Milne Edwards, 1842 (see Fouque 1948Fouque , 1954Goodbody 1974). Although an opening from the stomach has not yet been detected it probably will be found to occur in Clitella, as it is present in Didemnum lahillei and Diplosoma gelatinosum (see Fouque 1948Fouque , 1954. Further, in the two latter species, as in the present one, there are relatively few tubules of the pyloric gland encircling the duct. Nevertheless, despite the similarity of the gastric vesicle in these three species, all of which have relatively large zooids, a direct phylogenetic relationship is not implied, the present genus being distinguished from both Diplosoma gelatinosum and Didemnum lahillei by generic characters (see above).
The newly recorded specimen is only the second time the species has been collected. The zooids closely resemble those of the holotype, the only difference being the absence of spicules in the present colony. Kott, 2001 Diplosoma velatum Kott 2001, p 345;2004a, p 772.

Description
The species is the usual soft, encrusting sheet with the separate zooids held in groups at the surface by systems of branching test connectives that suspend them in the extensive common cloacal cavity between the thin surface and basal layers of test. The test contains granular bodies that make it cloudy. The whitish coloured (without black squamous epithelium), small zooids, with two testis follicles, have conspicuous oval terminal ampullae on the vascular stolons that extend out into the test from the ventral (concave) side of the gut loop.

Remarks
The species appears to be an indigenous one with a temperate geographic range across the southern coast of the continent. The species has been confused with the tropical D. translucidum (Hartmeyer, 1909). However, in addition to the distinguishing characters documented by Kott (2001), shallow longitudinal grooves have been found in the internal wall of the large stomach of D. translucidum.