OSTKACODA COLLECTED IN THE SOUTH SEA ISLANDS. 513 



gradually to the front; ventral margin sinuated in the middle, up-curved at each extremity. 

 Seen from above, compressed, ovate, widest in the middle, sides arcuate and tapering 

 evenly to the extremities, which are pointed and nearly equal ; not quite four times as 

 long as broad. Shell smooth and pellucid, marked with opaque patches. Length *55 mm. 

 Habitat. — Port of Noumea, 3-4 fathoms. 



Paradoxostoma retusum, n. sp. (PI. IV. fig. 20). 



Shell, seen from the side, oblong, flexuous, highest behind the middle, height equal to 

 nearly half the length. Anterior extremity narrow, evenly rounded ; posterior produced 

 above the middle into a rounded beak, from which it slopes downwards and forwards with 

 a full curve ; dorsal margin boldly arched, sinuated in front of the posterior extremity ; 

 ventral rather deeply sinuated in the middle, behind which it forms a compressed and 

 very convex marginal flange. Seen from above, compressed, widest in the middle, quite 

 four times as long as broad; lateral margins evenly curved, anterior extremity obtuse, 

 posterior acute. Shell pellucid, smooth, marked with opaque patches. Length '52 mm. 



Habitat. — Apia, Upolu, pools on inner reef. 



Section II. MYODOCOPA. 



Fam. CYPRIDINIDiE. 



Genus Philomedes, Lilljeborg. 



Philomedes vellicata, n. sp. (PI. IV. figs. 9, 10). 



Shell, seen from the side, oblong, subovate, greatest height in the middle, and equal to 

 half the length. Anterior extremity narrow, forming a rounded beak, beneath which is a 

 rather shallow notch ; posterior obliquely truncate, the obliquity looking upwards ; dorsal 

 margin moderately and evenly arched, rounded off in front, obscurely angular behind ; 

 ventral evenly convex, rounded at both ends. Seen from above, the outline is ovate, much 

 compressed, about three times as long as broad, with subparallel, slightly arcuate sides, 

 which are slightly constricted behind the middle ; obtuse in front, truncate behind, with a 

 stout median prominence. Surface of the valves smooth, very finely punctated with linear 

 dots, and marked behind the middle with a curved transverse furrow, which extends from 

 the dorsal margin to below the middle of the valve. Length 1*1 mm. 



Habitat. — Suva, pools on reef ; Levuka, between tide-marks. 



Genus Pleoschisraa* no v. gen. 



Shell very dense, surface pitted, smooth or tuberculated; seen from the side subcircular, 

 with a slight depression in place of a notch. 



Pleoschisma robusta, n. sp. (PI. IV. figs. 13, 14). 



Shell, seen from the side, nearly circular, highest in the middle, height equal to more 



* srAs'os", full ; <sxw(x.yi, a cleft. 

 VOL. XXXV, PART II. (NO. 14). 4 P 



