1923] POLYCHMTOUS ANNELIDS 3 



Admetella hastigerens Chamberlin 

 Admetella hastigerens Chamberlin, 1919, pp. 64-67, PI. ix, figs. 6-8. 



Chamberlin described this species from one specimen collected off 

 Panama in 581 fathoms. The Albatross collection contains five speci- 

 mens, none of which is complete, but it is possible by a comparison of the 

 five to get a fairly complete description. The largest was 100 mm. long 

 and 8 mm. wide, thus a trifle larger and narrower than Chamberlin's 

 specimen. The individual which is in most respects the best preserved is 

 50 mm. long. 



The prostomium agrees in general with Chamberlin's description, 

 but the "lateral extensions" are much more delicate than one would infer 

 from that description, being extremely thin, scale-like structures, which, 

 if the preservation has not been good, look very much like flakes of epi- 

 dermis that have loosened from the surface. The median tentacle has a 

 large ceratophore inserted into the dorsal middle line of the prostomium 

 and with a diameter about one-fourth that of the latter. It has a length 

 about equal to twice its diameter. The style is extremely delicate and 

 slender, extending to about somite 9. It broadens near the end and then 

 abruptly narrows to an acute apex. In the 50 mm. specimen the cera- 

 tophores of the lateral tentacles are hidden under the scale mentioned 

 above, while the styles are very short and slender, hardly longer than the 

 scale. In a specimen of twice this size the styles are relatively longer, 

 slightly swollen toward the end and with a sharp-pointed apex. There is 

 a faint trace of pigment around the swollen portion. The palps are more 

 slender than in Chamberlin's specimen and have acute apices. 



The dorsal and ventral cirri of the. first parapodium resemble the 

 median tentacle in form and size and are larger than the palps. The 

 ventral cirrus of the third parapodium is similar to these in form and size 

 but that of the fourth is much shorter and hardly longer than the para- 

 podium. Succeeding ventral cirri are progressively shorter and the 

 eighth is a slender, sharp-pointed structure attached to the ventral 

 face of the parapodium and not reaching the apex. The dorsal cirri are 

 broken in nearly all specimens, but those that remain agree in all respects 

 with those of the first two somites. The pharynx is protruded in a 100 

 mm. specimen. It is 12 mm. long, smooth throughout the greater part 

 of its length, but with roughenings toward the end. At the apex, above 

 and below, is a row of about fourteen soft papillae and three light-brown 

 teeth. 



A single elytron, the first or second, remains on the 100 mm. animal. 

 It is of sufficient size to cover, with its mate, the dorsal surface of the body 



