NATURAL SCIENCES OF PHILADELPHIA. 215 



Cheletropis crenilabris, Garr., pi. 2, fig. 18. 



Shell minute, ovate, thin, fragile, pellucid, shining, corneous ; 

 spire rather widely conical, a little more than half tlie length of 

 the shell, apex rather obtuse ; whorls 5, slightly convex, the first 

 two with very fine oblique raised lines, the last one large, swollen ; 

 suture faintly impressed ; aperture broadly oval, strongly effuse 

 at the base : peristome thickened, ribbed externally, and the lower 

 half crenulate on the edge ; columella slightly callous and some- 

 what twisted. 



Length 2 mill. 



Hah. Paumotus Seas. (Coll. Garrett.) 



Two perfect examples of this pelagic species were found on the 

 sands at the Paumotus Islands. It differs from the figure and 

 description of C Huxleyi^ Forbes. 



? RissoA viTREA, Garr., pi. 2, fig. 19. 



Shell minute, OA-ate, thin, pellucid, smooth, shining, white; 

 spire conical, obtuse ; whorls 5, strongly convex, last one large, 

 rounded; suture well impressed, margined ; aperture sub-circular, 

 nearl}' one-third the length of the shell ; peristome rather thick. 



Length li mill. 



Hah. Viti Isles. (Coll. Phil. Acad. Nat. Sciences.) 



Not uncommon in beach sand at Kiva Island. 



?RissoA LiTTORiN^FORMis, Garr., pi. 2, fig. 20. 



Shell small, ovate, smooth, shining, pellucid, white ; spire coni- 

 cal, obtuse ; whorls 5|^, strongly convex, last one very large, 

 rounded ; suture deeply impressed, slightly margined ; aperture 

 sub-circular, nearly one-third the length of the shell ; peristome 

 rather thick. 



Length, 2 mill. 



Hah. Viti Isles. (Coll. Garrett.) 



Two examples found with the preceding species, to which it is 

 closelj' allied. 



RissoA iNFRASTRicTA, Garr., pi. 2 fig. 21. 



Shell small, oblong, thick, shining, white, spire rather long, ob- 

 tuse; whorls 5, strongly convex, constricted at the base, and 

 slightly so next the suture, longitudinally ribbed, ribs large, ab- 

 ruptly terminating at the basal stricture; aperture roundly ovate 

 one-third the length of the shell ; peristome thick, with an external 

 rib. 



