NATURAL SCIENCES OF PHILADELPHIA. 209 



DESCRIPTIONS OF NEW SPECIES OF MARINE SHELLS INHABITING THE 



SOUTH SEA ISLANDS. 



BY ANDREW GARRETT. 



RissoiNA suPRAcosTATA, Garr., pi. 2, fig. 1. 



Shell elongate-oblong, sub-cylindrical, thin,, sub-pellucid, white 

 or corneous ; spire turreted, long, acute ; embryonal whorls 3, 

 smooth ; normal whorls T, convex, upper ones swollen above, the 

 first four with small longitudinal slightly oblique ribs ; whole sur- 

 face with regular crowded delicate raised strioe ; suture deeply im- 

 pressed ; aperture oblique, rather large, subovate, about one-third 

 the length of the shell ; peristome somewhat dilated, margined by 

 an external flat varix which curves upward over the umbilical re- 

 gion ; columella and parietal region covered witli a thin callus. 



Length 10 mill. 



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



A rare species of which we found fifteen examples in the upper 

 region of the larainarian zone. It belongs to the same group 

 with R. Gumingii and R. tenuistriata. It differs from the former 

 in its smaller size, more swollen whorls, and stouter varix behind 

 the outer lip. Gumingii has the longitudinal ribs cut by spiral 

 grooves. 



RissoiNA scuLPTiLis, Garr., pi. 3, fig. 2. 



Shell elongate-ovate, solid, shining, white ; spire long, gradu- 

 ally tapering from the body; whorls 9 ?, convex, latticed with lon- 

 gitudinal and transverse ribs, nodose at their points of intersec- 

 tion ; transverse ribs three on each whorl of the spire, five on 

 the body whorl, and their interstices crossed by very fine strife ; 

 suture deeply impressed ; aperture rather large, oblique, sub-ovate ; 

 peristome thick, somewhat dilated ; externally ridged at the basal 

 sinus; columella and parietal region with a rather thick deposit 

 of callus. 



Length 8^ mill. 



Hah. Viti Isles. (Coll. Garrett.) 



A very rare and beautiful species, of which we found but a single 

 specimen, very perfect except loss of apex. Its coarse latticed 

 surface will readily distinguish it. 



