BIPERFECTLT-KNOWN OSTEACODA. 191 



The secondary branch of the antenna in the female (fig. 12) is two-jointed, the last 

 joint short and bearing two long, but unequal seta; that of the left side in the male is 

 almost exactly similar, but on the right side bears as usual a very acutely angular hnok- 

 like claw (fig. 13). The ungues of the caudal lamina are five in number, very slender, 

 and scarcely at all curved (fig. 15). The copulatory organ in the male is unusually 

 broad and short (fig. 15). 



Eab. The gathering here noticed consists of about equal numbers of males and 

 females, and was taken at Cruz Bay. MuUer's specimens, five in number and all males, 

 were from the coast of Brazil. 



Genus Conchcecissa Claus. 

 CoNCH(ECissA cucuLLATA, sp. nov. (Plate XXIV. figs. 1-8.) 



Shell, seen from the side, oblong, much more than twice as long as broad ; greatest 

 width near the hinder extremity (fig. 1 j ; anterior extremity forming a narrow, sub- 

 cuneate, or hood-shaped prominence which is very acute at its apex, curvate on its 

 ventral, and perfectly straight on its dorsal margin, a shallow notch on its posterior 

 termination, from which point the ventral margin of the valve becomes boldly arcuate as 

 far as the posterior extremity, which is well rounded below but obtusely rounded at the 

 dorsal angle ; dorsal margin almost perfectly straight, but armed behind with a few 

 slender, backward-pointed spines ; postero-dorsal angle of the left valve (fio-s. 1 & 2) 

 produced into a very long spine-like process, below which is a broad curved sinus 

 terminated by a short papilliform process, beyond which the curve of the ventral 

 margin as far as the middle of its course is finely serrated ; dorsal anjjle of the rio-ht 

 valve rounded and spineless, but bearing a mammillated process like that of the opposite 

 valve ; there are groups of gland-cells connected with these processes and with the 

 dorsal spine, and similar, but snialler, cells are continued for a considerable distance 

 round the margin of the valves : seen from below the shell is elongated, subovate, 

 widest in the middle, three times as long as broad, tapering nearly to the extremities 

 which are sharply mucronate. Surface of the valves sculptured with regular, sub- 

 parallel wavy strise, from which are given off numerous delicate cross striee; the course 

 of many of the larger stride, especially on the posterior and ventral portions of the 

 valves, being marked by small irregularly-placed circular pits or areolae. The chewino-- 

 plates of the mandible (fig. 6) are armed with unusually short and blunt teeth, and are 

 only sparingly setiferous. Antennule of the fe^nale (fig. 3) bearing five (or sixl) equal 

 terminal setae, and one very short plumose hair ; frontal tentacle very slender, linear 

 and sharply pointed, and having a sharp needle-like hair alongside of it ; secondary 

 branch of the antenna of the female (fig. 5) short, ovate, bearing two short, spine-like 

 setae and a brush of five sensory filaments of moderate and equal length, that of the 



