400 ASTRALIIi\iE. 



Genus UVANILLA, Gray. 



Operculum flat, with two distinct, convex, radiating ribs, 

 the lower straight and nearly parallel to the edge, the 

 upper arched, sub-central, the axis imperforate and callous. 



Shell trochiform, acuminate, whorls flattened, fimbri- 

 ated, axis imperforate, base excavated ; aperture sub- 

 quadrangular ; inner lip acute, arcuated, sub-truncate in 

 front. 



Ex. U. finibriata, Lamarck, pi. 44, fig. 6. Opercu- 

 lum, U. olivacea. Wood, fig. 6, a, 6, h. Shell, U. olivacea, 

 fig. 6, c. 



Several species of this genus are known, the shells 

 being remarkable for their trochiform appearance and 

 the sharp keels or fimbriated edges of the whorls. 



Species of Uvanilla. 



acuta, Lam. latispina, Phil. 



brevispina, Lmn. occidentalis, Ghem. 



Buschii, Phil. olivacea, Wood. 



erythrophtlialmus, Phil. orichalcea, Koch. 



fimbriata. Lam. tentoriiformis, Jonas. 



gibberosa, Chem. tentorium, Anton. 



hexagona, Phil. ■ unguis, Wood. 



Genus PACHYPOMA, Gray. 



Operculum oblong, sub-quadrangular, very convex ex- 

 ternally. 



Shell trochiform, elevated, axis imperforate, whorls with 

 spinulose scales ; aperture sub-circular ; inner lip with a 

 prominent, exterior, curved callus, anteriorly sub-truncate. 



