Herdmania momus: Kott, 1985: 338 (part only).

Distribution

Type Locality. North-western Australia (Mary Anne Passage 21∞15¢S 115∞50¢E, 27 m, south of Barrow I., coll. R. J. Hannon 17.7.63, holotype WAM Z11771/ WAM 1199.83; Mary Anne Reef buoy, paratypes WAM Z11759/ WAM 212.82 (1).

Examined Material. North-western Australia (Rowley Shoals, WAM Z11768 / 1197.83 Z11769/1198.83(1) Z11770/1188.83(1); Dampier Archipelago, WAM Z11765 / 761.82(1); Cape Preston, WAM Z11763 / 974.85; Monte Bello Is, WAM Z11762 / 918.93; North-west Cape, WAM Z11761 / 924.83; Learmonth, WAM Z11760 / 1188.83; Shark Bay, WAM Z11756 / 1193.83 Z11757/1196.83; Cervantes WAM Z11779 /662.89.

Description

Specimens available from one to 6 cm (holotype) diameter, laterally flattened in preservative. Test thin, sometimes papery, white, slightly translucent, occasionally naked, but sometimes with sand completely encrusting it (WAM Z11762); or with Sea Grass (Amphibolis) fronds attached, forming a capsule around it (WAM Z11757 Z11779); or with a mixture of sand and other debris adhering (WAM Z11771).

Apertures on short divergent, naked siphons arising quite close together on the upper surface, atrial siphon the longer one, curved horizontally, branchial siphon directed obliquely upwards. Body wall adheres closely to inside of test. Circular muscles surround each siphon and longitudinal muscles extend along their length, to about halfway down each side of body wall. Longitudinal siphonal muscles divert to respective sides of body from mid-dorsal line. About 20 longitudinal branchial and about 12 longitudinal atrial muscles on each side. Atrial muscles on right cross over and exchange fibres with posterior half of dorsalmost branchial muscles anterior to gonad. Similar number of atrial and branchial muscles cross one another on left, although all but anterior three cover distal (dorsal) extent of distal limb of gut loop and gonad. Large circular dorsal tubercle has deep Ushaped slit with both horns turned or coiled in.

Up to ten branchial folds per side. Branchial formula of holotype: E1(3)1(10)2(14)3(20)9(27)6(20) 7(20)6(15)4(11)5DL. Dorsal lamina a narrow membrane with long pointed conical languets along its margin. Gut loop horizontal with usual compact liver in pyloric region enclosing left gonad. Anal border always divided into four shallow, smooth lips. Gonads, one per side, each a long, thick ovarian sac, only slightly undulating, with clumps of branched testis follicles around its margin, each clump connected to thick central common vas deferens by a vas efferens running at right angles to long axis of gonad. Oviducal opening large, shielded by circular to fan-shaped oviducal hood projecting from body wall over distal part of oviduct. Male opening on the tip of long cylindrical, distal part of vas deferens that projects free into atrial cavity. Occasionally body wall over this projection is produced into lobes or papillae around terminal aperture and in one specimen (WAM Z11761) a circle of pointed tentacle-like projections surrounds terminal aperture. Oviducal hood and projections around male aperture contain spines.

Remarks

The species is characterized by its smooth anal border with four shallow indentations and the projecting tip of the vas deferens. The tapering conical dorsal languets and narrow dorsal lamina, oviducal hood, projections around the male opening, central common vas deferens with a single aperture, clumps of male follicles and simple U-shaped slit on the dorsal tubercle with horns rolled in resemble Herdmania fimbriae, although the latter species has a regularly undulating ovary, fewer longitudinal branchial vessels, shorter longitudinal muscle bands and a deeply lobed anal border. Occasionally in H. fimbriae the tip of the vas deferens projects into the atrial cavity, but its free part is much shorter than in the present species. The species is distinguished from H. pallida by its oviducal hood, anal border and relatively few dorsal internal longitudinal branchial vessels between the dorsal lamina and dorsal fold on each side. Herdmania insolita has shorter longitudinal muscles than the present species, fewer internal longitudinal branchial vessels on and between the folds and it lacks the freely projecting distal end of the vas deferens found in the present species.

The known range of the present species is between Cervantes and Rowley Shoals on the north-western Australian coast. Herdmania fimbriae is recorded from the western end of the Great Australian Bight to Bowen (Queensland). So far, neither of these species has been recorded from Torres Strait, the Arafura Sea, south-western Australia, and north-eastern Australia north of Bowen.