CALLOrOMA. 395 



Geuus PRISOGASTER, Morch. 



Operculum ovate, convex, granular, with an elevated, 

 grooved rib extending from the nucleus to the hinder 

 margin, nearly parallel to the straight or inner edge. 



Shell solid, turbinate, axis imperforate ; spire elevated, 

 whorls transversely grooved ; aperture ovate, longer than 

 wide ; columella with a parallel groove ; outer lip margined 

 with white, lirate internally. 



Ex. P. niger, Gray, pi. 43, fig. 6. Operculum, P. 

 niger, fig. 6, a, G, h. Shell, P. niger, fig. 6, c. 



The animal of this genus, figured by M. D'Orbigny, 

 appears to be furnished with a single, elongated, posterior 

 filament, numerous shorter, anterior, tentacular filaments 

 on the lateral membrane of the foot, and two conspicuous. 

 cirrhi on the sides of the opercular lobe. 



Genus CALLOPOMA, Gray. 



Operculum with a broad central, and three or five sub- 

 marginal, spiral ribs, outer ribs toothed. 



Shell turbinate, thick, axis imperforate ; spire elevated, 

 whorls smooth, or with transverse nodulose or squamose 

 ridges ; aperture circular, expanded ; inner lip broad, flat- 

 tened, excavated, produced anteriorly, and furnished with 

 a parallel, curved groove. 



Ex. C. fluctuatum. Gray, pi. 43, fig. 7. Operculum, 

 C. fluctuatum, fig. 7, a, 7, b. 



This genus somewhat resembles Lunella, but the axis 

 is imperforate the aperture is dilated, and the operculum 



