Eunice tribranchiata McIntosh 1885

Eunice tribranchiata McIntosh, 1885

Eunice tribranchiata McIntosh, 1885:297, pl. 21A: figs. 6, 7.—Fauchald, 1986:258, figs. 71–75.

Eunice torresiensis McIntosh, 1885:270–272, figs. 32, 33, pl. 37: figs. 18–21, pl. 19A: figs. 12, 13 [in part].

MATERIAL EXAMINED.—Holotype and paratype, BM(NH) ZK. 1885.12.1.205, 2 syntypes of Eunice torresiensis, BM(NH) ZK.1885.12.1.193, Challenger sta 186, Torres Strait, 10°30′S, 142°18′E, 15 m, coral sand.

COMMENTS ON MATERIAL EXAMINED.—An account of the material of this species can be found in Fauchald (1986:258); the description below is based on one of the two syntypes removed from the material of E. torresiensis.

DESCRIPTION.—Holotype a posterior fragment of 90 median and posterior setigers. Specimen described and illustrated incomplete with 35 setigers, 31 mm long; maximal width 7 mm at setiger 10; length through setiger 10, 13 mm. Other specimen with 18 setigers; length 15 mm; maximum width 8 mm; length through setiger 10, 11 mm. Body cylindrical, abruptly tapering anteriorly.

Prostomium (Figure 110e) distinctly shorter and narrower than peristomium, less than as deep as peristomium. Prostomial lobes frontally rounded, dorsally inflated; median sulcus deep. Antennae in a horseshoe, with A-I isolated by a gap, similar in thickness. Ceratophores ring-shaped in all antennae, without articulations. Ceratostyles tapering, with up to 6 cylindrical articulations of varying lengths in A-III. A-I to posterior peristomial ring; A-II and A-III to setiger 1. Peristomium as wide as anterior part of body, cylindrical, with distinct muscular lower lip. Separation between rings well marked dorsally and less distinct ventrally; anterior ring ∼ of total peristomial length. Peristomial cirri to middle of anterior peristomial ring, slightly inflated basally, with 5 articulations.

Maxillary formula (illustrated in McIntosh, 1885, plate 37: fig. 20) 1+1, 4+4, ?+0, 6+6, 1+1; Mx III absent in illustration, but here assumed present in specimen.

Branchiae (Figure 110a) present, pectinate, distinctly longer than notopodial cirri, not reduced in mid-body region, flexible. Branchiae from setiger 4 or 5 to end of fragments. All branchiae with 2 or more filaments; maximum 8 filaments. Branchial stems tapering, flexible; filaments longer than stems, digitiform.

Neuropodial acicular lobes symmetrically triangular; aciculae emerging at midline. Pre- and postsetal lobes low, transverse folds. First 5 ventral cirri very large, digitiform. Ventral cirri basally inflated from about setiger 6. Inflated bases large, scoop-shaped (subacicular hooks emerging at bases of scoops when they start); narrow tips tapering. Notopodial cirri basally slightly inflated with 2 or 3 long, indistinct articulations.

Limbate setae slender, marginally serrated. Pectinate setae (Figure 110c) flat, flaring with thick shafts. All teeth similar in length and thickness; ∼20 teeth present. Shafts of compound falcigers (Figure 110b) long, essentially un-tapering, marginally smooth. Appendages slender, tapering, bidentate. Proximal teeth larger than distal teeth, triangular and directed laterally or slightly distally. Distal teeth tapering, very nearly erect. Guards asymmetrically bluntly pointed; mucros absent. Pseudocompound falcigers and compound spinigers absent. Aciculae paired, black, distally tapering, straight; cross-sections round. Subacicular hooks (Figure 110d) black, bidentate. Hooks first present from setiger 30, present in all setigers thereafter, always single (except for replacements). Heads small; teeth similar in size. Proximal teeth directed laterally, curved. Distal teeth triangular, directed distally. Guards short and truncate.

UNKNOWN MORPHOLOGICAL FEATURES.—Structure of Mx III and its relationship to left Mx IV; pygidium and anal cirri.

EXPECTED STATES OF UNKNOWN MORPHOLOGICAL FEATURES.—Mx III short, forming part of distal arc with left Mx II.

CHARACTERS USED IN PREPARATION OF KEY NOT SCORED.—Inappropriate Characters: 56. Unknown Characters: 1, 2, 4, 6, 13, 14, 36–38, 40, 42, 57–60, 63, 74, 78.

ASSUMED STATES FOR PURPOSE OF PREPARING KEY.—37,1; 38,1.