86 Memoirs of the Indian Museum. [Vol. II, 



than the fourth. The fully developed rami of the posterior cirri armed like those 

 of the first pair, except that on the greater number of the joints (all but the first few 

 at the base) they bear only one transverse pair of bristles on each joint with a number 

 of fine hairs between them ; hairs at the tip of the joints behind few and short. The 

 posterior rami of the fifth and sixth cirri very fine, having 17 and 15 joints respec- 

 tively, while the anterior rami have a very large number ; the hairs on the posterior 

 rami short and extremely fine, confined to the tip of the distal joint (which is small and 

 cylindrical) and to the distal end of the posterior margin of the last ten joints. Anal 

 appendages very slender, consisting of about nine joints and extending slightly beyond 

 the distal end of the pedicel of the sixth cirri ; the bunch of hairs at the tip short and 

 sparse. Penis moderately long and slender, cylindrical, pointed at the tip, minutely 

 annulated, bearing a few scattered hairs on the surface and a bunch of similar hairs 

 at the tip. 



Mouth parts. — Mandibles not buUate, bearing a sparse row of minute, rounded, 

 chitinous teeth. Maxillce narrow ; the biting edge with a rather shallow incisure, at 

 the base of which there is a small, conical projection ; the outermost spine by far 

 the largest. Mandible with five teeth, the inner angle being dichotomous ; the outer 

 tooth the largest, pectinate at its base on the inner margin, separated from the 

 other teeth by a deep but not very broad incisure ; second, third and fourth teeth 

 subequal, the innermost tooth very small ; second tooth pectinated at the base on 

 the inner margin. 



Habitat. — Nicobar Islands, on floating wood [de Roepstorff). Ten specimens in 

 rather bad condition. 



This species bears a close external resemblance to Gruvel's figures of his Alepas 

 indie a from Singapore. It appears, however, to differ considerably from that species, 

 with which I formerly confused it, in the structure of its cirri and mouth parts. The 

 largest specimen I have seen measures 40 mm. in total length, but the peduncle in all 

 is somewhat curved. 



Subfamily PŒCILASMATINM. 

 Key to the Genera. 



1. Valves fully calcified, covering the whole or nearly the whole 

 of the capitulum. 



[a) Carina not expanded laterally at the base . . . . Pœcilasm.a. 



{h) Carina expanded laterally at the base . . . . Megalasma. 



2. Valves more or less degenerate and separated from one 

 another ; at least one calcified valve as a rule present. 



{a) Scutum split into two segments, which diverge from one 



another above, or reduced to a vertical linear rudiment . . Dichelaspis. 



Genus Pcecilasma, Darwin (1851). 

 lyCpadidse with 3, 5 or 7 fully calcified, approximate valves. The scutum broad, 

 entire or split into two vertical segments, of which the occludent segment 



