REPORT ON THE ANNELIDA. 
529 
one is seen. Compared with the hook of Placostegus assimilis, the transverse striae are 
much wider, while the hook on the whole is less. 
The tube is comparatively smooth. 
The hooks of this species seem to l)e minutely toothed, much more so than in the 
known forms. Their structure, indeed, approaches that of the genus Om'plialo'poma of 
Mdrch,^ but the conical nature of the operculum is characteristic. 
Spirohranchus, Blainville. 
Spirohranchus occidentalis, n. sp. (PI. LV. fig. 10 ; PI. XXIXa. figs. 31, 32). 
Hahitat. — Dredged at Station 33 (off the Bermudas), April 4, 1873 ; lat. 32° 21' N., 
long. 64° 35' W.; depth, 435 fathoms; surface temperature, 68°‘0 ; sea-bottom, coral 
mud. It was attached to a tube of Placostegus assimilis. 
The branchiae have a sinuous arrangement, but such is probably due to their retrac- 
tion within the tube on preservation in spirit, and they are only a little shorter than the 
body (the total for both being about 7 mm.). The radioles are marked by transverse 
wrinkles at somewhat regular intervals, and the tip of each ends in a smooth filiform 
process, slightly thickened distally. The terminal pinnae reach as far outward as the 
latter. 
The operculum had a short, horny, conical process (shaped somewhat like a hook) 
projecting from its surface, but it broke off before a figure could be made. This process 
was situated on an elevation near the edge most distant from the branchiae, as usual in 
the group. The operculum is horny, blackish-brown in colour, and nearly circular. It is 
supported by a hollow membranous process, which is only a little constricted interiorly, 
so that it is nearly cylindrical, the upper part of the peduncle being flattened out into a 
broad fan-shaped end to meet it. The cephalic collar is ample, presenting dorsally a 
large lateral lamella on each side of the median fissure, and being thrown into many frills 
ventrally, though no fissure occurs. 
The anterior bristles (PI. XXIXa. fig. 31) somewhat resemble those of the previous 
Vermilia, having a short tapering tip with well-marked wings, the edges of which are 
serrated. 
The anterior hooks (PL XXIXa. fig. 32) have an elevated crown and a very long 
serrated edge, no less than eleven or twelve teeth occurring above the great fang. More- 
over, the latter is produced in a remarkable way, and the tip is bifid. The dorsal line 
has a deep incurvation, but the ventral margin is nearly straight. There is a small 
truncated prow below the notch under the great fang. The striae on the body of the 
1 Op. cit, Revisio critica Serpnlidaruiii, p. 421. 
(ZOOL. CHALL. EXP. — PART XXXIV. — 1885.) 
LI 67 
