IMPEEFECTLT-KNOWN OSTEACODA. 183 



Cyclasteeope brevis (G. W. Miiller). (Plate XXIV. figs. 16-22.) 



Asterope brevis G. W. jMiiller, " Neue Cypridiuiden/' Zoologisch. Jahrbiich. vol. v. p. 239, pi. xxv. 

 fig. 10, pi. xxvi. fig. 7, pi. xxvii. figs. 7-10, 15, 16. 



Shell of the female seen from the side (fig. 16) almost circular, the length being only 

 about one-seventh longer than the width, antennal notch situated slightly below the 

 middle of the somewhat narrowed anterior extremity; posterior extremity boldly rounded, 

 as is also the ventral margin ; dorsal margin well arched, but flatter than the ventral ; 

 the right valve is slightly overlapped by the left throughout its entire circumference: 

 seen from above the outline is elongated, ovate, nearly twice as long as broad, 

 extremities obtusely rounded, rather narrower in front than behind. Shell-surface 

 smooth; colour brown. Length 3-3 mm. The fifth joint of the antennule (fig. 17) 

 has five marginal papilliform humps ; the external margins of the antennal joints 

 (fig. 18) are produced into very large, stout spines ; the principal swimming-setse are 

 profusely ciliated and have, at intervals of five or six rings throughout the greater 

 part of their length, delicate marginal spines (fig. 19) ; secondary branch of the antennae 

 (fig. 20) two-jointed, the first joint bearing five or six marginal hairs, the last a 

 single long, ringed seta. Postabdominal laminte armed with four finely pectinated 

 claws (fig. 22). 



Hab. St. Thomas, West Indies. Very few specimens, all females. 



The male is unknown ; the one female specimen described by Miiller was taken off 

 the coast of South America (Pernambuco) : in all essential respects it seems to agree 

 with those here noticed. 



Cyclasteeope similis, sp. nov. (Plate XXIII. figs. 25-29.) 



Shell of the female, seen from the side, subelliptical, height equal to nearly two- 

 thirds of the length (fig. 25) ; antennal notch rather wide and shallow, situated in the 

 middle of the evenly rounded anterior extremity ; posterior extremity as wide as the 

 anterior, evenly rounded ; dorsal margin almost rectilinear for the greater part of its 

 length, ventral moderately arcuate; both extremities fringed with short hairs; surface 

 smooth. Length 5 mm. Penultimate joint of the antennule (fig. 20) having a single 

 large papilliform hump and a few fine marginal hairs: outer margins of the antennal 

 joints, except the first, produced into long stout spines (tig. 27), first swimming-seta 

 short and plumose, none of the setae bearing marginal spines ; secondary branch 

 (fig. 28) indistinctly three-jointed, the last joint bearing a single ringed seta, the first 

 five marginal hairs. Male unknown. 



Hab. One specimen only, from a depth of 8 fathoms in Java Sound. 



This species approaches Asterope brevis G. W. Miiller in the single hump of the 

 fifth antennular joint, but diff'ers widely in the shape of the shell and the characters of 

 the antenna! swimming-setae. 



