ODOXTOSYLLIS G-IBBA. 183 



(Claparede), slightly diminished anteriorly, and more distinctly tapering posteriorly. It 

 is bright green at Dinard, with a transverse band of greyish granulation in each segment 

 (De St. Joseph). Yellowish-green (Marenzeller). Body terminated by two cirri. 

 Marenzeller and Marion and Bobretzky observe that the armed region of the proboscis is 

 found in the fifth setigerous segment, and it has six teeth under a glandular mass of the 

 fibrous region of the organ. The proventiculus occurs in the eighth setigerous segment, 

 and it is twice as long as the former. 



The foot (Plate LXX, fig. 12) is comparatively short and bluntly bifid at the tip, the 

 bristles issuing between the papillae. Two pale spines pierce the tip superiorly and their 

 ends are peculiarly bent so as to form a short, blunt beak anteriorly, whilst a kind of heel 

 projects posteriorly in some, as apparently first indicated by Marenzeller. The tip is 

 indeed somewhat T-shaped, especially in the posterior segments (Plate LXXIX, fig. 5). 

 The bristles are translucent, with the shafts slightly curved, dilated, and bevelled at the 

 tip, which is finely spinous. The terminal piece (Plate LXXIX, fig. 6) is short, with a 

 bold and sharp hook at the tip, and a concave, spinous edge in front. 



The ventral cirrus is broadly lanceolate, and does not reach the tip of the setigerous 

 region. 



Reproduction. — An example captured on April 23rd at Plymouth is laden with 

 nearly ripe sperm-cells. The segmental organs are green (Fage 1 ). 



The habits of this form would seem to resemble those of O.fulgurans, and Marion 

 and Bobretzky found it brilliantly phosphorescent. 



3. Odontosyllis gibba, Claparede, 1863, var. Robertian^. Plate XLIX, figs. 3 and 4; 

 Plate LIX, fig. 14 and Ua— head; Plate LXX, fig. 13— foot; Plate LXXIX, 

 fig. 7 — bristle. 



Specific Characters. — Head small, rounded or bluntly conical, with two reddish eyes, 

 confluent or separated, on each side, the anterior the wider apart. Two short anterior 

 tentacles and a median with a dark tip in front of the eyes. Tentacular cirri dark. Body 

 about half an inch long, most distinctly tapered posteriorly. Segments 43 — 48. Of a 

 pale brown or fawn colour, with a whitish stripe interrupted by three or four brownish 

 touches along the dorsum, and a transverse white belt extending to the bases of the feet 

 on the seventh segment. Ventral surface of a pale brown hue with dark touches in front. 

 Gribbous segment succeeding the head is somewhat semicircular, and bears two clavate 

 cirri each with a white ring on the dilated region. Terminal segment has two short and 

 somewhat clavate cirri with a white touch at the tip. Foot uniramous in so far as there 

 is only one spine. Dorsal region elevated, giving rise to a clavate cirrus, dilated towards 

 the tip, which has a white ring, and with a slender terminal process. The cirrus is simply 

 clavate or fusiform in other examples. Setigerous region separated by a sulcus, its dorsal 

 margin convex, and terminating externally in two conical papillse. -Bristles long, slender, 

 and translucent, dilated distally, and with a shoulder and a bevelled edge. Terminal 

 process short, very slightly diminished at the tip, which has a simple hook. 



1 ' Ann. Sc. Nat./ 9 e ser., iii, p. 316. 



