Revision of Chone Krøyer, 1856 (Polychaeta: Sabellidae) from North America and descriptions of four new species

The present study deals with the revision of type and non‐type material from 12 species of Chone Krøyer, 1856 (Polychaeta: Sabellidae) that have been described from North America: C. albocincta Banse, 1972, C. aurantiaca (Johnson, 1901), C. bimaculata Banse and Nichols, 1968, C. ecaudata (Moore, 1923), C. gracilis Moore, 1906, C. magna (Moore, 1923), C. minuta Hartman, 1944, C. mollis (Bush in Moore, 1904), C. picta (Verrill, 1885), C. princei McIntosh, 1916, C. ungavana Chamberlin, 1920, and C. veleronis Banse, 1972; and the formal description of four new species: Chone eiffelturris n. sp., Chone paramollis n. sp., Chone quebecensis n. sp., and Chone trilineata n. sp. Chone princei is redescribed and transferred to the genus Jasmineira Langerhans, 1880; C. ungavana is declared incertae sedis; C. bimaculata is reinstated; C. minuta is synonymized with C. ecaudata, and C. mollis is recorded for the Pacific coast of Panama.

Copenhagen (ZMUC). The revision of Chone americana, C. farringtonae, C. perkinsi, and C. uebelackerae was published recently by Tovar-Hernández (2005); here these species are only included in order to be properly compared with the remaining species described from North America.
Histological sections were made at the Laboratorio de Invertebrados of the Facultad de Ciencias, Universidad Nacional Autó noma de México (UNAM). After paraffin embedding, most serial sections were cut (mostly 7 mm) and stained with haematoxylineosin. Drawings were made with a camera lucida. Samples of chaetae and uncini were processed and examined after final dehydration in two changes of 100% ethanol at the Laboratorio de Microscopía Electró nica de Barrido (Facultad de Ciencias, UNAM). CO 2 was used to critical-point dry the specimens, which were then mounted on stubs with platinum tape and coated with gold (200 Å thicknesses) before examination with a Cambridge 250 scanning electron microscope. Some samples were examined at the Laboratorio de Microscopía Electró nica de Barrido (ECOSUR Tapachula).
Branchial lobes and branchial crown. Insertion of the branchial crown not exposed beyond collar ( Figure 1A). Branchial crown length 5-7.5 mm (2-10). Radioles: seven to eight pairs (five to ten). Radioles with median pinnules two times longer than more proximal pinnules. Radiolar tips long. The palmate membrane extends three-quarters the length of the branchial crown (it almost reaches the radiolar tips). Lateral flanges broad ( Figure 1G). Dorsal lips triangular, erect, without mid-rib. Ventral lips rounded, about three-quarters the length of the dorsal lips. Ventral radiolar appendages: one pair, as long as branchial crown.
Abdomen. Abdominal segments: 31-48 (26-47). Anterior segments: two transverse rows of elongate, narrowly hooded chaetae, chaetae from upper row half as long as chaetae in lower row; uncini with the main fang surmounted by five regular rows of teeth in frontal view, equal in size, occupying one-half the length of main fang, main fang not extending beyond breast, breast rectangular ( Figure 1E). Posterior segments: 1-2 very elongate, narrowly hooded chaetae, 25% longer than in anterior segments; modified uncini with the main fang surmounted by six to seven regular vertical rows of teeth equal in size, occupying three-quarters the length of main fang, main fang not extending beyond breast, breast rectangular ( Figure 1F). Pygidium with triangular posterior margin ( Figure 1D).
Methyl green staining. The anterior margin of the collar is not coloured; the posterior half of the collar is darker than anterior half; anterior half with grooves and dark spots, the triangle above the ventral shield is not coloured. Thorax and anterior abdomen with epidermis completely glandular, stains uniformly, dorsally ( Figure 1A), ventrally ( Figure 1B), and laterally ( Figure 1C). Posterior end with dark glands ( Figure 1D). After 1 day, body stays stained, except the posterior abdomen.

Remarks
Chone albocincta, C. veleronis, and C. eiffelturris n. sp. (see below) are distinguished from other species of the genus by the whitish segmental rings in the thorax and anterior abdomen (Table II). Chone albocincta can be distinguished from C. veleronis and C. eiffelturris n. sp. by the following: the glandular ridge on the second chaetiger is broad ventrally, dorsally it extends to the anterior margin of the intra-notochaetal groove (ventrally greatly broadened extending into the third chaetiger, dorsally narrow in C. veleronis; narrow, same width in C. eiffelturris n. sp.); the ventral shield of collar is rounded with an anterior whitish triangle and two postero-lateral grooves (ventral shield of collar horseshoe-shaped, three times longer than wide in C. veleronis; 2.5 times longer than wide in C. eiffelturris n. sp.); short branchial lobes in C. albocincta and C. eiffelturris n. sp. (long in C. veleronis).
Branchial lobes and branchial crown. Insertion of the branchial lobes not exposed beyond collar. . . Radioles with median pinnules two times longer than proximal pinnules. Radiolar tips short ( Figure 2J). The palmate membrane extends about three-quarters the length of branchial crown. Lateral flanges broad ( Figure 2H, J). Dorsal lips broadly rounded in frontal view, as long as wide, without mid-rib, resembling the ventral lips, longer than wide in dorso-lateral view. Dorsal pinnular appendages: (two pairs) united by a palmate membrane (pm) ( Figure 2I). Ventral lips rounded, as long as wide, about one-quarter the length of dorsal lips. Ventral radiolar appendages: (eight short pairs).
Thorax. Chaetiger 1: two groups of eight elongate, narrowly hooded chaetae. Chaetigers 2-8: notopodia-two rows of elongate, narrowly hooded chaetae ( Figure 2O); one anterior row with bayonet chaetae, two posterior rows with symmetrical, paleate chaetae with a very short mucro, sometimes minute or not discernible ( Figure 2L-N); neuropodia-two irregular rows of 25 acicular uncini per torus, facing in the same direction, the oldest upper parts of the tori have only one row (one-quarter the length of tori), main fang surmounted by six rows of teeth, second tooth enlarged, located in the midline; dentition covering one-quarter the main fang length ( Figure 2K). Glandular ridge on chaetiger 2: narrow.
Methyl green staining. The entire body turns uniformly green. The anterior half of the collar is not coloured, posterior end dark. Anterior half of the ventral shield of collar not coloured, posterior half dark.

Remarks
Megachone was synonymized in Chone by Banse (1972) by the presence of spatulate chaetae in the type species. Banse (1972) recorded irregular orange-red spots in collar and anterior segments in the holotype. These spots are actually whitish and iridescent.
Chone aurantiaca, C. gracilis, C. magna, C. mollis, C. picta, and the type species (C. infundibuliformis) constitute a group of species (Group I) that have anterior and posterior abdominal uncini of similar shape (Table III). This is in contrast with a second group (Group II) in which the posterior abdominal uncini are modified (Table II).
Chone aurantiaca, C. farringtonae, and C. magna have a long posterior peristomial ring collar: in C. aurantiaca and C. farringtonae it is 2.5 times as long as second chaetiger (three times longer in C. magna). Chone aurantiaca and C. magna have uniform abdominal uncini throughout and narrow glandular ridge on chaetiger 2 (posterior abdominal uncini modified and broad glandular ridge in C. farringtonae). Chone aurantiaca can be distinguished from C. magna by having short radiolar tips (long in C. magna), broad radiolar flanges (narrow in C. magna), and ventral shield of collar horseshoe-shaped (rounded in C. magna).
In the case of Chone aurantiaca, C. mollis ( Figure 19B), and C. infundibuliformis the glandular ridge occupies only the external half of the ventral glandular epithelium; whereas dorsally, the glandular ridge occupies only a very small area. For Chone aurantiaca and C. infundibuliformis, Tovar-Hernández and Sosa-Rodríguez (2006) determined that the glandular ridge is composed of strongly differentiated acidophil glandular cells, tubularshaped with granulose secretions. From both taxonomic and systematic standpoints, it is recommended that the characterization of the external shape and the extension within the epithelium of the glandular ridge be taken into account as species diagnostic characters.

Revision of Chone from North America
Branchial lobes and branchial crown. Insertion of the branchial lobes exposed beyond collar ( Figure 3A). Branchial crown length 5 mm. Radioles: eight pairs. Radioles with median pinnules two times longer than proximal pinnules. Radiolar tips extra long ( Figure 3D, E). The palmate membrane extends to three-quarters the length of branchial crown. Lateral flanges broad ( Figure 3D, E). Dorsal lips three times longer than wide, without a mid-rib. Dorsal pinnular appendages: two short pairs. Ventral lips rounded, as long as wide, about one-quarter the length of dorsal lips. Ventral radiolar appendages: two short pairs. Peristomium. Anterior peristomial ring lobe slightly exposed beyond collar dorsally, distally bilobed ( Figure 3B). Posterior peristomial ring collar: antero-dorsal margin incised ( Figure 3A); entire length of mid-dorsal collar margins forms two prominent lobes, covering a narrow gap; small dorsal pockets ( Figure 3A); lateral and ventral margins entire ( Figure 3A, B); ventral margin slightly higher than dorsal. Ventral shield of collar trapezoidal, two times wider than long ( Figure 3B). Ratio of posterior peristomial ring collar length versus chaetiger 2 length, in lateral view: 1:1.
Abdomen. Abdominal segments: 41. Anterior segments: two rows of five elongate, narrowly hooded chaetae ( Figure 3L); uncini with the main fang surmounted by three or four rows of teeth equal in size, second tooth enlarged, dentition occupying one-half the length of main fang; main fang not extending beyond breast, breast rectangular ( Figure 3K). Posterior segments: three very elongate, narrowly hooded chaetae, 25% longer than in anterior segments; five to eight modified uncini per torus with the main fang surmounted by six to seven regular rows of teeth equal in size, occupying three-quarters the length of main fang, main fang not extending beyond breast, breast rectangular ( Figure 3M-P). Pygidium with rounded posterior margin ( Figure 3C). (1968)  Methyl green staining. Paratypes with histolysis, when stained, the colour is quickly eliminated. Ventral shield of collar with an anterior whitish line. Two dark rectangles located on lateral sides of anterior peristomial ring collar.

Remarks
The paratypes reviewed have pygidium with rounded posterior margin, not pointed as Banse and Nichols depicted (1968, Figure 2C). Banse (1972, p 466) synonymized C. bimaculata Banse and Nichols, 1968 with Chone duneri Malmgren, 1867 (described from Spitzbergen). The main reason for describing C. bimaculata was the presence of a glandular ridge on chaetiger 2; however, this structure is a diagnostic character for Chone. Chone duneri has been recorded from several latitudes and is considered to be a species with a very wide distribution; however, according to Cochrane (2000) only materials from the Pechora Sea (in the southeastern and northern parts of the Barents Sea) agree with the original description of Malmgren (Spitzbergen) and the redescription of Hofsommer (1913) (Jutland) for Chone duneri. She recommended revising the records of C. duneri because Spitzbergen is heavily influenced by Atlantic water masses and the subsequent records contain some discrepancies in the diagnostic characters observed (Madeira by Langerhans 1880 and Mediterranean Sea by Giangrande 1992).
In this study C. bimaculata is recognized as a valid species based on unique characters summarized below that separate it from C. duneri (based on additional material from Norway and Scotland) and comparison with records by Cochrane 2000). Both species have the insertion of the branchial lobes and the bilobed anterior peristomial ring lobe exposed beyond the collar as well as radiolar tips extra long (comprising approximately a third of the length of radioles). Chone bimaculata differs from C. duneri in that lateral flanges are narrow (broad in C. duneri ); the antero-dorsal margin of posterior peristomial ring collar is incised (not incised in C. duneri ); the entire length of mid-dorsal collar margins forms two prominent lobes, covering a narrow gap (broad gap in C. duneri ); the anterior peristomial ring lobe is partially exposed beyond collar dorsally (completely exposed in C. duneri ); the ventral shield of collar is trapezoidal (horseshoe-shaped in C. duneri ); modified posterior abdominal uncini (anterior and posterior abdominal uncini similar in C. duneri ) and pygidium with rounded posterior margin (triangular in C. duneri ).
Chone ecaudata (Moore, 1923) (  (8) Description (based on C. ecaudata holotype; in parentheses variation of paratypes of C. ecaudata and C. minuta) Colour, body shape, and size. Body cream coloured. Trunk cylindrical, posterior abdomen dorso-ventrally flattened. Holotype complete (almost broken in the middle of the body), paratypes incomplete. Body length 3.5 mm (5-9), width 0.75 mm (0.5-0.75). Tubes not preserved in type material, but Moore (1923) recorded that the basal half lacks covering, being thin and transparent, the distal half increasingly coated with a soft, grey, flocculent silt in which minute fragments of shells are scattered. Tubes from MMS Phase II materials flexible, constructed with fragments of shells, algae, and rocks. Branchial lobes and branchial crown. Insertion of the branchial lobes not exposed beyond collar. Branchial crown length 4 mm (1.5-2.5). Radioles: six pairs (six to nine). Radioles with distal pinnules three times longer than median pinnules. Radiolar tips long (Figures 4E, 5A-D). The palmate membrane (pm) extends to three-quarters the length of branchial crown. Lateral flanges (fl) broad ( Figures 4A, 5C, D). Dorsal lips (dl) three times longer than wide, erect, without mid-rib ( Figure 4F), triangular in transversal section on the branchial crown base ( Figure 6A). Dorsal pinnular appendages: one to three (three to four) short pairs occupying one-quarter of the branchial crown length. Ventral lips rounded, as long as wide, about one-quarter the length of dorsal lips. Ventral radiolar appendages (vra): three pairs, the inner and middle ones about one-half the length of branchial crown ( Figure 4G), the remainder about one-quarter the length of branchial crown.
Abdomen. Abdominal segments: 42 (24-26). Anterior segments: two rows of five to six elongate, narrowly hooded chaetae, chaetae from upper row 50% shorter than chaetae in lower one; 10-12 uncini per torus with the main fang surmounted by three regular vertical rows of teeth equal in size, second tooth enlarged, dentition occupying one-half the length of main fang, older (dorsalmost) uncini smaller than younger uncini (ventralmost), main fang not extending beyond breast, breast rectangular ( Figure 5F). Posterior segments: one to two very elongate, narrowly hooded chaetae, 25% longer than in anterior segments, making an angle with the shaft at the base of the hood; five to eight modified uncini per torus with the main fang surmounted by six to seven regular vertical rows of teeth equal in size, occupying three-quarters the length of main fang, older (dorsalmost) uncini smaller than younger uncini (ventralmost), main fang not extending beyond breast, breast rectangular ( Figure 5G). Pygidium with rounded posterior margin ( Figure 5E).
Gametes. Holotype mature female, with oocytes from third thoracic segment to posterior abdomen. Paratype mature female, with oocytes in thorax. Additional females with oocytes (oo) in thorax (Figures 4C, 5I) and abdomen (USNM 40722,. Histology of dorsal lips. The branchial crown is vascularized by two large blood vessels (bv), innervated (n) at the base of each branchial lobe, and supported by lateral bars or horns of radiolar skeleton (rs) ( Figure 6A). The dorsal lips (dl) are vascularized by a plexus of small blood vessels (bv) that run along the lip as a strongly branched network ( Figure 6B, C); each blood vessel is surrounded by coelomic chambers (co) ( Figure 6C). The dorsal lips have conjunctive tissue (ct) extending along the outer margin of the lip, but there is no extension of the branchial skeleton. Two types of simple epithelium are present in dorsal lips: columnar (gce) and cubic ( Figure 6B). The columnar epithelium covers the external/ outer margin of the lips ( Figure 6B, C), includes ciliated cells and type ''a'' glands ( Figure 6C), and is covered by a cuticle. The cubic epithelium covers the internal/inner margin of the lip ( Figure 6B, C), there are no ciliated cells.
Methyl green staining. The anterior margin of the collar has a granular pattern ( Figure 4A, E, F). The ventral shield of the collar stained completely, except for the anterior margin ( Figure 4A, B, E-G). Dark areas around the thoracic notopodia are separated by a spotty stained longitudinal band. The epidermis is completely glandular and stains uniformly ventrally in thorax and abdomen ( Figure 4A); dorsally colourless in thorax and collar ( Figure 4D). The posterior abdomen has a granular pattern. Bodies of specimens fixed inside their tubes have a cross-sectional rectangular appearance after methyl green staining. (1923) described Chone ecaudata in the genus Jasmineira by the absence of palmate membrane; however, Hartman (1942a, p 135) transferred this species to Chone. Banse (1972) synonymized Chone minuta Hartman, 1944 and C. ecaudata, finding that there are no differences between the diagnostic characters for the two species; this conclusion is confirmed here, since type materials from both species and several additional samples reviewed have no differences in their external general morphology, chaetae and uncini, histology of the dorsal lips, or distribution and size of gametes. Banse (1972), in his figure 6e, shows well-developed ventral shields of a specimen from British Columbia identified as C. ecaudata; however, the shape of the collar and anterior thoracic segments illustrated do not correspond with C. ecaudata, and the specimen figured is probably a species of Euchone. The ventral thoracic segments in C. ecaudata and C. quebecensis n. sp. are completely swollen due to the fact that the glandular columnar epithelium (gce) is broad or high ( Figure 19A, C), in contrast with other species such as C. aurantiaca, C. infundibuliformis (Tovar-Hernández and Sosa-Rodríguez 2006, Figure 12), and C. mollis ( Figure 19C), in which the glandular columnar epithelium in ventral thoracic segments is low. In C. ecaudata and C. quebecensis n. sp. the ventral thoracic segments look like a mat when treated with methyl green, but they cannot be considered ventral shields as in members of Euchone or other sabellid genera such as Demonax or Sabellastarte, in which the shields are well developed and completely distinctive due to their rectangular shape, the presence of intersegmental grooves, and the less coloured glandular epidermis of the lateral sides of the body. Additional material. Chone aurantiaca (Johnson, 1901) [MCZ 1933. Chone magna (Moore, 1923)  Description (based on holotype, in parentheses variation observed in paratypes)
Abdomen. Abdominal segments: 53 (43-51). Anterior segments: two transverse rows ofelongate, narrowly hooded chaetae, chaetae from upper row half as long as chaetae in lower row; uncini with the main fang surmounted by three regular rows of teeth in frontal view, second tooth enlarged, dentition occupying half the length of main fang ( Figure 7J), main fang not extending beyond breast, breast rectangular; single, narrow glandular ridge per segment, more evident than those in thorax. Posterior segments: one or two very elongate, narrowly hooded chaetae, directed upwards, modified uncini with the main fang surmounted by six to seven regular vertical rows of teeth equal in size ( Figure 7K), occupying three-quarters the length of main fang, main fang not extending beyond breast, breast rectangular. Pygidium with triangular posterior margin ( Figure 7A).
Methyl green staining. Anterior margin of the ventral shield of collar not coloured ( Figure 7A, C). Body stains uniformly ( Figure 7A-C). Posterior end with a granular pattern ( Figure 7A).

Etymology
The specific name refers to the peculiar shape of the ventral shield of the collar, which is Eiffel Tower-shaped. Derived from the Latin turris, meaning tower.

Remarks
Chone eiffelturris n. sp., C. paramollis n. sp., C. aurantiaca, C. magna, C. mollis, and C. picta have paleate chaetae with a minute mucro, not easily discernible (Tables II, III). However, Chone eiffelturris n. sp. and C. paramollis n. sp. have the modified posterior abdominal uncini typical of Group II, in comparison with C. aurantiaca, C. magna, C. mollis, and C. picta the abdominal uncini are of similar shape throughout (Group I). Chone eiffelturris n. sp. has extremely long radiolar tips (long in C. paramollis n. sp.); the palmate membrane extends more than three-quarters the length of branchial crown, almost reaching radiolar tips (three-quarters in C. paramollis n. sp.); ventral shield of collar is Eiffel Tower-shaped (horseshoe-shaped in C. paramollis n. sp.) and glandular ridges are present in thorax and anterior abdominal segments (absent in C. paramollis n. sp.). Chone eiffelturris n. sp. is unique in having extremely long radiolar tips, ventral shield of collar Eiffel Tower-shaped and glandular ridges in thorax and anterior abdomen. Other species with glandular ridges in thorax and anterior abdomen are Chone albocincta and C. veleronis (see remarks on C. albocincta). Chone mollis and Chone eiffelturris n. sp. are species with wide distribution in California, Western Mexico, and the Pacific coast of Panama.   (1); 000009-25 (1); 000007-12 (4).

Description (based on holotype, in parentheses variation observed in paratypes)
Colour, body shape, and size. Body cream coloured (brown in USNM 40723) with an iridescent epicuticle. Trunk cylindrical. Holotype complete, but pygidium and some radioles are broken, branchial crown almost separate from the body. Body length 21 mm (5-12 mm), width 1.5 mm (0.5-1.5). Tube hyaline.
Thorax. Chaetiger 1: two groups of nine elongate, narrowly hooded chaetae. Chaetigers 2-8: notopodia-two rows of nine elongate, narrowly hooded chaetae; one anterior row with four to five bayonet chaetae ( Figure 8K); two posterior rows with five symmetrical, paleate chaetae with short mucro ( Figure 8L); neuropodia-two irregular rows (one row) of 19 (13) acicular uncini per torus, facing in the same direction, the oldest upper parts of the tori have only one row (one-quarter of the torus length), main fang surmounted by four rows of teeth, second tooth enlarged, located in the midline, dentition occupying a quarter the length of main fang ( Figure 8J). Pre-and post-chaetal lobes well developed. Glandular ridge on chaetiger 2: narrow.
Abdomen. Abdominal segments: (24-43). Anterior segments: two transverse rows of very elongate, narrowly hooded chaetae; uncini with the main faing surmounted by three rows of teeth occupying one-half the length of main fang, main fang not extending beyond breast, breast rectangular ( Figure 8M). Posterior segments: very elongate, narrowly hooded chaetae; uncini similar to those in anterior abdomen, but larger ( Figure 8N). Pygidium with rounded posterior margin ( Figure 8G).
Gametes. Holotype female with oocytes in thorax and abdomen; paratype immature.
Methyl green staining. Anterior end of the ventral shield of collar not coloured, posterior end dark ( Figure 8A). The epidermis is completely glandular (looks like a mat) and stains uniformly in thorax and abdomen, dorsally and ventrally ( Figure 8E-G).

Remarks
Chone gracilis Moore, 1906  . It may be used as a valid name. The holotype of Chone gracilis has the ventral margin of the collar incised probably, due to a regeneration process. However, in paratype and additional material it is entire. Deep-water specimens from Oregon have abdominal elongate narrowly hooded chaetae, extremely long. Chone gracilis is unique among the species of Chone distributed in North American waters in having medium-length radiolar tips. Among species in Group I, Chone gracilis and C. infundibuliformis have a short mucro; however, the ventral margin of the collar is higher than dorsal margin in C. gracilis, and slightly higher in C. infundibuliformis.
Chone magna (   Description (based on holotype, number in parentheses correspond to paratypes and non-type material) Colour, body shape, and size. Body cream coloured, covered by an iridescent layer of epicuticle. Trunk cylindrical ( Figure 9C, E, F). Holotype fragmented in three parts (without branchial crown, posterior abdomen damaged as well as a few chaetigers). Body length 8.2 mm (54-71), width 3 mm (2.5-6). Tubes unknown.
Branchial lobes and branchial crown. Insertion of the branchial lobes not exposed beyond collar (exposed only when anterior margins of collar are reflexed). Branchial crown length (16-18 mm). Radioles: (29) pairs. Radioles with median pinnules two times longer than basal ones. Radiolar tips long (3.5 mm) ( Figure 9D, P). The palmate membrane extends to three-quarters the length of branchial crown. Lateral flanges narrow ( Figure 9P). Dorsal lips (dl) broadly rounded, longer than wide, without mid-rib ( Figure 9I, M). Dorsal pinnular appendages (dpa): (five to six short and median pairs). Ventral lips small, rounded, as long as wide, about one-half length of dorsal lips. Ventral radiolar appendages: one to three pairs, the inner one about three-quarters the length of branchial crown, the remainder about one-quarter the length of branchial crown.
Thorax. Chaetiger 1: two groups of 10 elongate, narrowly hooded chaetae. Chaetigers 2-8: notopodia-two rows of 8-10 elongate, narrowly hooded chaetae ( Figure 9J); one anterior row with eight to nine bayonet chaetae; two posterior rows with 11 symmetrical, paleate chaetae without mucro (a very short hair-like mucro in additional material) ( Figure 9K); neuropodia-two irregular rows of 26-46 acicular uncini per torus ( Figure 9G), facing in the same direction, the oldest upper parts of the tori have only one row (one-quarter the length of tori), main fang surmounted by four rows of teeth, second tooth enlarged, located in the midline, dentition occupying a quarter the length of main fang ( Figure 9L). Pre-and post-chaetal lobes well developed. Glandular ridge on chaetiger 2: narrow.
Abdomen. Abdominal segments: 42 (62-72). Anterior segments: two rows of 6-10 elongate, narrowly hooded chaetae, chaetae from upper row half as long as chaetae in lower row; 10-12 uncini per torus with the main fang surmounted by three rows of teeth, occupying half the length of main fang, older (dorsalmost) uncini smaller than younger uncini (ventralmost), main fang not extending beyond breast, breast rectangular with a triangular anterior tip ( Figure 9N). Posterior segments: one or two very elongate, narrowly hooded chaetae, 50% longer than in anterior segments; five to eight uncini per torus, similar to those in anterior segments, but smaller ( Figure 9O). Pygidium with rounded posterior margin ( Figure 9H).
Gametes. Holotype male with sperm in posterior abdomen, spermatozoa nucleus barrelshaped (1.5 times longer than wide), acrosome sub-triangular and two large, rounded mitochondria.
Methyl green staining. Anterior end of the ventral shield of collar not coloured, posterior end dark. Collar coloured only in the basal half. Body coloured uniformly dorsal and ventrally.

Remarks
Euchone magna was transferred to Chone by Hartman (1969), see details in Banse (1972, p 473). Chone magna is included in the Group I (species with anterior and posterior abdominal uncini with similar shape; Table III). Chone magna and C. picta have a long posterior peristomial ring collar, three times longer than second chaetiger; but C. magna has long radiolar tips (short in C. picta) and narrow radiolar flanges (broad in C. picta).

Description (in parentheses variation of specimens LACM-AHF 003259)
Colour in preserved material, body shape, and size. Body brown coloured with an iridescent layer of epicuticle (separated from the body wall Branchial lobes and branchial crown. Insertion of the branchial lobes not exposed beyond collar. Branchial crown length 8 mm (8-10). Radioles: 17 pairs (13-16). Pinnules from middle region twice as long as more proximal pinnules. Radiolar tips long, elongate ( Figure 10G). The palmate membrane extends to three-quarters the length of branchial crown. Lateral flanges broad. Dorsal lips broadly rounded in frontal view, as long as wide, without a mid-rib, resembling the ventral lips. Dorsal pinnular appendages: (five to eight) short pairs united by a palmate membrane. Ventral lips rounded, as long as wide, about one-half of the dorsal lips length. Ventral radiolar appendages (vra): one to five pairs, onequarter to one-half the length of branchial crown ( Figure 19B).
Peristomium. Base of the peristomium composed of two lateral horns of basal central skeleton (bcs) surrounding the mouth (mo); anterior peristomial ring lobe (lo) exposed beyond collar, distally triangular, elongate ( Figure 10B-D, F). The base of the posterior peristomial ring collar is supported by basal lateral skeleton (bls). Antero-dorsal, lateral, and ventral margins of the posterior peristomial ring collar entire ( Figure 10A-D); ventral margin slightly higher than dorsal ( Figure 10C); entire length of mid-dorsal margins forms a narrow gap; dorsal pockets well developed. Ventral shield of collar swollen, inside and outside of the collar wall ( Figure 10B), horseshoe-shaped, two times wider than long ( Figure 10B, D), divided by a median-longitudinal line in large specimens ( Figure 10B). Ratio of posterior peristomial ring collar length versus chaetiger 2 length, in lateral view: 2:1.
Narrow glandular ridge on chaetiger 2, it occupies a quarter of the epithelium in longitudinal section ( Figure 19B).
Abdomen. Abdominal segments: 42 (41-43), two transverse rows of five to six elongate, narrowly hooded chaetae, chaetae from upper row half as long as chaetae in lower one; uncini with the main fang surmounted by four regular vertical rows of teeth equal in size, occupying one-half the length of main fang, older (dorsalmost) uncini smaller than younger uncini (ventralmost), main fang not extending beyond breast ( Figure 10N), breast rectangular. Posterior segments: one or two very elongate, narrowly hooded chaetae; uncini similar to those in anterior abdomen ( Figure 10O). Pygidium with rounded posterior margin ( Figure 10E).
Gametes. Holotype and specimens from Pacific Panama females with oocytes (oo) in thorax ( Figure 19B).
Methyl green staining. The epidermis is completely glandular and stains uniformly in thorax and abdomen, dorsally and ventrally ( Figure 10A-C). The ventral shield of collar is not coloured in the anterior margin ( Figure 10B, D). Posterior end with granular pattern ( Figure 10E).

Remarks
Metachone mollis was established as having thoracic paleate chaetae lacking a mucro; however, Fauvel (1927) transferred this species to Chone, arguing that because the size and length of the mucro varies greatly between species it cannot have generic significance. Reexamination of type material confirmed the presence of a very short hair-like mucro in complete chaetae in holotype. Chone aurantiaca, C. magna, C. picta, and C. mollis have paleated chaetae with mucro minute or absent (Table III). In C. mollis, the ratio of posterior peristomial ring collar length versus chaetiger 2 length is 2:1 (2.5:1 in C. aurantiaca, 3:1 in C. magna and C. picta); the ventral margin of the posterior peristomial ring collar is slightly higher than dorsal (very much higher in C. aurantiaca, C. magna, and C. picta); the radiolar flanges are narrow (broad in C. aurantiaca); and the entire length of mid-dorsal margins forms a narrow gap (broad C. magna and C. picta). Like Chone eiffelturris n. sp., C. mollis is distributed in California, Western Mexico, and Pacific coast of Panama.
Branchial lobes and branchial crown. Insertion of branchial lobes not exposed beyond collar ( Figure 11A, B). Branchial crown length 5 mm (4). Radioles: eight pairs (seven to eight). Radioles with median pinnules twice the length of proximal pinnules. Radiolar tips long ( Figure 11G). The palmate membrane extends to three-quarters the length of branchial crown. Lateral flanges narrow. Dorsal lips (dl) triangular, elongate, erect, without mid-rib ( Figure 11F). Dorsal pinnular appendages: two pairs. Ventral lips rounded, as long as wide, about one-quarter the length of dorsal lips. Ventral radiolar appendages: one pair, occupying one-half the length of branchial crown.
Peristomium. Anterior peristomial ring lobe triangular at their base, then digitiform, not exposed beyond collar. Posterior peristomial ring collar: antero-dorsal margin forming well-developed dorsal pockets, entire length of mid-dorsal collar margins forms a narrow gap ( Figure 11C); lateral and ventral margins entire ( Figure 11A, B, D); ventral margin slightly higher than dorsal ( Figure 11B). Ventral shield of collar horseshoe-shaped, swollen, as wide as long ( Figure 11D). Ratio of posterior peristomial ring collar length versus chaetiger 2 length, in lateral view: 2:1.
Abdomen. Abdominal segments: 46 (37-43). Anterior segments: two transverse rows of elongate, narrowly hooded chaetae, chaetae from upper row half as long as chaetae in lower row; uncini with the main fang surmounted by three regular rows of teeth in frontal view, second tooth enlarged, dentition occupying half the length of main fang, main fang not extending beyond breast, breast rectangular ( Figure 11K, L). Posterior segments: one or two very elongate, narrowly hooded chaetae, modified uncini with the main fang surmounted by six to seven regular vertical rows of teeth equal in size, occupying threequarters the length of main fang, main fang not extending beyond breast, breast rectangular ( Figure 11M, N). Pygidium with triangular posterior margin ( Figure 11E).
Gametes. Holotype female with oocytes in thorax and mid-abdominal region, different sizes.
Methyl green staining. The epidermis is completely glandular and stains uniformly in thorax and abdomen, dorsally and ventrally, except the anterior margin of collar ( Figure 11A-C).
The anterior end of the first ventral glandular shield is not coloured, lateral sides of ventral shield of collar dark ( Figure 11A-C). Posterior end granular ( Figure 11E). After 24 h specimens lost colour; only two glandular rings per segment are visible.

Etymology
Specific name refers to the similarity between this species and Chone mollis.

Remarks
The collar segment of Chone paramollis n. sp. resembles Chone mollis; however, C. paramollis n. sp. has modified posterior abdominal uncini (Group II), which are not modified in C. mollis (Group I); the ventral shield of collar is as long as wide in C. paramollis n. sp. (two times wider than long in C. mollis); the anterior peristomial ring lobe not exposed beyond collar (exposed in C. mollis); the posterior peristomial ring collar length is two times longer than first chaetiger length (1.5 in C. mollis). Chone paramollis n. sp. and C. eiffelturris n. sp. are unique among species of Chone from Group II in having paleate chaetae with a minute or indiscernible mucro: C. paramollis n. sp. has long radiolar tips (extremely long in C. eiffelturris n. sp.); the palmate membrane extends three-quarters of the branchial crown length (more than three-quarters, almost reaching radiolar tips, in C. eiffelturris n. sp.); ventral shield of collar horseshoe-shaped (''A''-shaped in C. eiffelturris n. sp.) and lacking glandular ridges in thorax and anterior abdominal segments (present in C. eiffelturris n. sp.).

Redescription
Colour, body shape, and size. Body cream coloured. Verrill (1885): ''color of the body greenish, specked with bright red, most so posterior and anteriorly, on the collar the red predominates. Branchiae transparent greenish white, with transverse spots of flake-white and bright red; bases light red''. Trunk cylindrical. Body length 20.7-40.7 mm, width 2-2.5 mm.
Branchial lobes and branchial crown. Insertion of the branchial lobes not exposed beyond collar dorsally ( Figure 12A). Branchial crown length 6-11 mm. Radioles: 12-15 pairs. Radioles with median pinnules two times longer than more proximal pinnules. Radiolar tips short. The palmate membrane extends up half the length of branchial crown. Lateral flanges broad. Dorsal lips (dl) two times longer than wide, rounded, erect, without mid-rib ( Figure 12E). Dorsal pinnular appendages: one to three short pairs. Ventral lips rounded, as long as wide, about one-quarter the length of dorsal lips. Ventral radiolar appendages: one to three pairs, the inner one about three-quarters the length of branchial crown, the remainder about one-quarter the length of branchial crown.
Branchial lobes and branchial crown. Insertion of the branchial lobes (bl) exposed beyond collar ( Figure 13A, B). Branchial crown length 7 mm (6-7). Radioles: 10 pairs (8-13). Radioles with median pinnules three times longer than more proximal pinnules. Radiolar tips long ( Figure 13E). The palmate membrane extends to three-quarters the length of branchial crown. Lateral flanges broad ( Figure 13E). Dorsal lips three times longer than wide, erect, without mid-rib. Dorsal pinnular appendages: one to three short pairs, united by a palmate membrane. Ventral lips rounded, as long as wide, about one-quarter the length of dorsal lips. Ventral radiolar appendages: one to three pairs, the inner one as long as three-quarters the length of branchial crown, the remainder about one-quarter the length of branchial crown. Peristomium. Anterior peristomial ring lobe exposed beyond collar ( Figure 13B-D), distally bilobed ( Figure 13D, F). Posterior peristomial ring collar: antero-dorsal margin deeply incised, forming two well-developed dorsal pockets ( Figure 13A), two dorsal, oval glandular shields (ogs) ( Figure 13A, B), entire length of mid-dorsal collar margins forms a narrow gap ( Figure 13A); lateral and ventral margins entire ( Figure 13C, D); ventral margin slightly higher than dorsal ( Figure 13B, C). Ventral shield of collar swollen, horseshoe-shaped, two times wider than long ( Figure 13D). Ratio of posterior peristomial ring collar length versus chaetiger 2 length, in lateral view: 2:1.
Abdomen. Abdominal segments: 46 (42-46). Anterior segments: two transverse rows of five to six elongate, narrowly hooded chaetae ( Figure 13M, V), chaetae from upper row half as long as chaetae in lower row ( Figure 14G); 10-12 uncini per torus, older (dorsalmost) and younger uncini (ventralmost) with the main fang surmounted by six regular rows of teeth in frontal view, equal in size, occupying three-quarters the length of main fang ( Figure 14B), main fang not extending beyond breast ( Figure 14O), breast rectangular. Posterior segments: one or two very elongate, narrowly hooded chaetae, 25% longer than in anterior segments ( Figure 14H), making a small angle with the shaft at the base of the hood ( Figure 13N, U); five to eight modified uncini per torus with the main fang surmounted by six to seven regular vertical rows of teeth equal in size ( Figure 14C), occupying threequarters the length of main fang, older (dorsalmost) uncini smaller than younger uncini (ventralmost), main fang not extending beyond breast, breast rectangular. Ventral, glandular, whitish band on posterior abdomen (gb) ( Figure 13G). Pygidium with triangular posterior margin ( Figure 13G).
Gametes. Females with oocytes polyhedron-shaped in thorax and abdomen ( Figure 15B), diameter 37.5-56.25 mm. Sperm in posterior abdominal chaetigers, spermatozoa rectangular nucleus (two times longer than wide), acrosome sucking-shaped (occupying one-quarter the length of nucleus) and two small, rounded mitochondria.
Methyl green staining. Anterior end of the ventral shield of collar not coloured, posterior end dark. Dorsally, there is no colour in collar, chaetigers 1 and 2; then each segment is divided into four dark rectangles by the presence of the faecal groove, inter-segmental and intra-notochaetal and neurochaetal grooves. Ventrally, each segment has a median, longitudinal dark band; lateral sides are coloured uniformly. Laterally, the collar has two large, rectangular spots ( Figure 13C). Pygidium stays darker for several days.
Histology. The ventral, posterior abdominal glandular band (gb) in Chone quebecensis n. sp. is a complete whitish band in preserved material ( Figure 13G), pink with however, features of branchial crown and peristomium were not detailed or illustrated, and type material of C. teres was not available in time to be included in this revision.
Branchial lobes and branchial crown. Insertion of the branchial lobes exposed beyond collar ( Figure 16A, B, E). Branchial crown length 2.2 mm (3). Radioles: six pairs. Radioles with distal pinnules three times longer than more proximal pinnules. Radiolar tips long. The palmate membrane extends to three-quarters the length of branchial crown. Lateral flanges narrow. Dorsal lips three times longer than wide, erect, without mid-rib. Dorsal pinnular appendages: one short pair, united by a palmate membrane. Ventral lips rounded, small. Ventral radiolar appendages absent.
Abdomen. Abdominal segments: 24 (26). Anterior segments: two transverse rows of elongate, narrowly hooded chaetae ( Figure 16L). Posterior segments: one or two very elongate, narrowly hooded chaetae; modified uncini with the main fang surmounted by six to seven regular vertical rows of teeth equal in size ( Figure 16F, G), occupying threequarters the length of main fang, main fang not extending beyond breast, breast rectangular. Pygidium with triangular posterior margin ( Figure 16A).
Methyl green staining. The epidermis is completely glandular and stains uniformly in thorax and abdomen, dorsally and ventrally, except the anterior margin of collar. The anterior end of the first ventral glandular shield and the extensions of the glandular ridge on chaetiger 2 are not coloured ( Figure 16A-E).

Etymology
The specific name is Latin, meaning three-lined; and refers to the peculiar shape of the glandular ridge on chaetiger 2.

Description (based on paratypes)
Colour in preserved material, body shape, and size. Body and base of the branchial crown cream coloured. Glandular ridge brown or orange. Glandular ridges yellow in segments  from anterior part of abdomen ( Figure 17A). Body depressed for all its length, with a ventral compression along last 14 abdominal segments. Body length 7-9 mm, width 0.35-0.5 mm. Tubes unknown.
Colour in fresh material. Base of the branchial crown cream coloured. Mid-dorsal collar margins red/orange, colour extending towards the dorsal lips. Radioles cream coloured in the basal half, then two distal red bands occupying the length of three pinnules, colour extending into pinnules. One pair of dorsal pinnular appendages with white spots on the basal half. Flanges and body wall transparent. Orange oocytes in thorax and anterior abdomen. Glandular ridge on chaetiger 2, and anterior abdominal ridges white [LACM, AHF, Santa Monica Bay, SMB-LACSD, Sta. 8D17, LH04-438].
Branchial lobes and branchial crown. Insertion of the branchial lobes exposed beyond collar laterally ( Figure 17A, G). Branchial crown length 3-4 mm. Base of the branchial crown long, about one-quarter the length of branchial crown ( Figure 17C-F). Radioles: five to six pairs. Radioles with median pinnules twice as long as distal pinnules. Radiolar tips long ( Figure 17J). The palmate membrane extends to three-quarters the length of branchial crown (almost reaching the radiolar tips). Lateral flanges broad ( Figure 17J). Dorsal lips triangular, elongate, erect, three times longer than wide, without mid-rib (dl) ( Figure 17I). Ventral lips rounded (vl) and about one-half the length of dorsal lips ( Figure 17I). Ventral radiolar appendages: one pair occupying one-half the radiole length (vra) ( Figure 17I). Dorsal pockets not developed.
Peristomium. Base of the peristomium composed of two lateral horns of basal central skeleton (bcs) surrounding the mouth (mo); anterior peristomial ring lobe (lo) not exposed beyond collar, distally entire, triangular ( Figure 17H). The base of the posterior peristomial ring collar is supported by basal lateral skeleton (bls). Posterior peristomial ring collar: dorsal, ventral, and lateral margins entire (Figure 17A, C-G); ventral margin higher than dorsal ( Figure 17A, G); entire length of mid-dorsal collar margins forms a narrow gap ( Figure 17D, E). Ventral shield of collar swollen, extending to the second thoracic segment, horseshoe-shaped, three times longer than wide ( Figure 17C, F). Ratio of posterior peristomial ring collar length versus chaetiger 2 length, in lateral view: 2:1.
Thorax. Chaetiger 1: two groups of elongate, narrowly hooded chaetae. Chaetigers 2-8: notopodia-two irregular rows of elongate, narrowly hooded chaetae; one anterior row with bayonet chaetae; two posterior rows with symmetrical; paleate chaetae with medium-sized mucro ( Figure 17K, L); neuropodia-one row of acicular uncini with the main fang surmounted by four rows of teeth equal in size, occupying half the length of main fang ( Figure 17M). Glandular ridge on chaetiger 2 (gr2): ventrally, the glandular ridge is sunglasses-shaped, extending to the first half of the third segment; dorsally, inverted Ushaped. The ridge is located near to the superior margin of second segment dorsally and ventrally, on the sides it is located near to the inferior margin of the second segment, under noto-and neurochaetae (Figure 17A, C-G).
Abdomen. Abdominal segments: 33-35. Anterior segments: one glandular ridge in most anterior segments, then two ridges per segment (gr) ( Figure 17A); two transverse rows of elongate, narrowly hooded chaetae; uncini with the main fang surmounted by four regular rows of teeth in frontal view, equal in size, occupying half the length of main fang, main in size, breast reduced to narrow swelling, handles long ( Figure 18G). Posterior segments: very elongate, narrowly hooded chaetae, 25% longer than in anterior segments; uncini similar to those in anterior abdomen. Pygidium with a triangular, posterior margin.
Gametes. Lectotype female with oocytes in anterior abdomen, visible through the body wall. Paralectotype female, oocytes from the second thoracic segment to the last thoracic segment.
Methyl green staining. The anterior margin of collar is not coloured dorsally, ventrally, or laterally. The ventral shield of collar is dark coloured. The posterior and basallateral margins of collar are dark. The ventral shield of the first thoracic chaetiger is dark with anterior longitudinal grooves ( Figure 18A). Each thoracic segment is uniformly coloured ventrally ( Figure 18A); laterally, each segment has a dark rectangle in the upper and lower side of the torus ( Figure 18B); dorsally, colourless.

Remarks
In this study, a lectotype and two paralectotypes are designated from syntypes according to Article 74.4, International Commission on Zoological Nomenclature (2000). Chone princei is redescribed and transferred to the genus Jasmineira due to the fact that the original description lacked some critical details diagnostic for Jasmineira. The redescription provided here shows that in J. princei: (1) insertion of the branchial lobes is exposed beyond collar; (2) pinnules are similar-sized along radioles; (3) palmate membrane is absent; (4) radiolar flanges are narrow; (5) dorsal lips are elongate, triangular with radiolar appendages; (6) dorsal pinnular appendages are absent; (7) anterior peristomial ring lobe is not exposed beyond collar; (8) dorsal pockets are well developed with vascular loops in the peristomium; (9) abdominal uncini have the main fang covered by teeth of equal size, breast reduced to narrow swelling, and handles long; and (10) oocytes are distributed in thorax and anterior abdomen.
Jasmineira is often confused with Fabrisabella Hartman, 1969, because both have abdominal uncini with a reduced narrow breast and long handle; however, they differ in that Fabrisabella lacks dorsal pinnular appendages and bayonet chaetae; both are present in Jasmineira (Fitzhugh 1989). , in his description of Chone princei, referred to a ''glandular tubular organ'' located at the dorsal peristomium; this structure is called ''vascular loops'' in the redescription given here. The vascular loops are circular cameras situated dorsally in each side of the peristomium; inside each camera there is an S-or C-shaped vessel; their structure and function has not been studied yet, but it is very probable that they are vascularized by the central blood vessel. The vascular loops have also been recorded in the genus Fabrisabella (Fitzhugh 1989), and in some specimens of Euchone analis ( Figure 18O).  Additional material. Chone infundibuliformis Krøyer, 1856[ZMUC POL-1749USNM-376, paralectotype;BMNH 82.5.12.33, paralectotype].

Description
Holotype dried out, complete but torn in thorax and abdomen. Branchial crown as long as half of the body length. Insertion of the branchial lobes exposed beyond collar, anterior peristomial ring lobe triangular, exposed beyond collar. Ventral margin of collar higher than dorsal. Dorsal margins forming two deep pockets. Radioles with broad flanges, radiolar tips short. Ventral shield of collar swollen. Thoracic uncini distributed as irregular double rows in tori, four rows of teeth above the main fang, hood present ( Figure 18I). Bayonet chaetae ( Figure 18H). Anterior abdominal uncini with four to five rows of teeth above the main fang, occupying half the length of main fang, main fang not extending beyond breast, breast rectangular ( Figure  anterior ones, but smaller ( Figure 18L, M). Pygidium rounded ( Figure 18N). Holotype female with oocytes in thorax.

Remarks
Holotype is dried out, no additional material is available, and there are no new records of this species since its description in 1920. From the holotype, only a few characters were recognized, two of them also being present in C. infundibuliformis. Chone ungavana and C. infundibuliformis have short radiolar tips, broad flanges and thoracic uncini distributed in two irregular rows in each torus. However, in C. ungavana the anterior peristomial ring lobe is exposed beyond the collar (not exposed in C. infundibuliformis), and branchial lobes exposed beyond the collar (not exposed in C. infundibuliformis). At this time it is not possible to recognize the validity of C. ungavana due to the dehydration of the only available material.

Discussion
Two groups of the species can be recognized in Chone Krøyer, 1856: the first one is a homogeneous group integrated with the type species C. infundibuliformis and composed of species with anterior and posterior abdominal uncini of similar shape (Chone-type) ( Table III). In species of this group, hundreds of small oocytes are distributed in the thorax and abdomen. The dorsal lips are broadly rounded, without mid-rib, vascularized by a plexus of a few small blood vessels, and supported by hyaline cartilage with no extension of the branchial skeleton. The margin of the anterior peristomial ring lobe is triangular and entire. The glandular ridge on chaetiger 2 is homogeneously narrow; and the glandular, columnar epithelium in the ventral thoracic segments is narrow and low (not swollen).
The second group is composed of species with modified, posterior abdominal uncini (as rasp-shaped plates or Amphicorina-type) (Table II). This kind of modified uncinus has a main fang surmounted by several regular, vertical rows of small teeth of equal size that occupy at least three-quarters the length of the main fang, and a poorly developed rectangular or sub-rectangular breast, in contrast to an anterior segment uncinus with a few rows of unequal-sized teeth occupying less than half the length of the main fang and a well-developed breast (Tovar-Hernández and Sosa-Rodríguez 2006). In species in this group, a few large oocytes are distributed in the thoracic and abdominal segments. The dorsal lips are triangular, elongate, erect, without mid-rib, vascularized by a plexus of several small blood vessels, and supported by hyaline cartilage with no extension of the branchial skeleton. The anterior peristomial ring lobe can be triangular, digitiform, or bilobed. The glandular ridge on chaetiger 2 varies among species of this group: it can be a complete or an incomplete band; a narrow or broad homogeneous band; broad or narrow dorsally, laterally, or ventrally; with a mid-ventral projection; or ventrally greatly broadened, sunglasses-shaped, and extending to the third chaetiger. Glandular ridges in the thorax and anterior abdomen can be present. The glandular, columnar epithelium in the ventral thoracic segments is broad and high (swollen, but without ventral shields).
According to Rouse and Fitzhugh (1994), intratubular brooders tend to be small-bodied, with few relatively large eggs (as in members of Group II) whereas broadcast spawners are large-bodied with several small eggs (as in members of Group I). Bick and Randel (2005) studied the ontogenetic variations in Euchone analis. In their study they argued that juveniles have fewer teeth above the main fang on abdominal uncini than adult specimens. However, the number of teeth in profile above the main fang of anterior and posterior abdominal uncini in juvenile and mature individuals of Chone infundibuliformis (and others species in Group I) is the same. This pattern also occurs in posterior abdominal uncini of juvenile and mature specimens of species in Group II. If the presence/absence of modified, posterior abdominal uncini (Amphicorina-type) is a feature that is not due to ontogeny, the modified uncini could be a plesiomorphic character for Group II and such variation could result in splitting the genus. However, the revision of type and non-type materials for all the remainder species of Chone is needed in order to place them within this framework of sabellid evolution.