CRYPTOSTOMA. 



GENERIC CHARACTER. 



Shell ear-shaped, univalve, spiral, very much depressed ; 

 spire hardly elevated above the general curvature, lateral ; 

 aperture very large, oblong, entire, embracing a portion 

 of the preceding volution ; labrum simple ; volutions two 

 or three ; columella short, spiral : nacre none ; muscular 

 impressions two, lateral, distant ; a slightly revolving, ele- 

 vated line on the inner surface ; operculum none. 



Animal tongue shaped, chielly formed by a very long, 

 and very thick foot, which is narrower and massive be- 

 fore, truncated behind, canal iculated on each side and 

 widely margining on all sides the contorted visceral mass, 

 which is very small, slightly convex above, and covered by 

 an interior shell ; head depressed ; mouth very small, con- 

 cealed under the anterior and superior margin of the foot^ 

 tentacula two, compressed and appendiculate at base ; a 

 large branchial pecten ; male organ under the right ten- 

 taculum ; mantle without emargination. 



OBSERVATIONS. 



That able anatomist Blainville was the first to detect the 

 diflTerence between the animal of the much depressed spe- 

 cies of the genus Sigaretus, Adans , and of those with a 

 more elevated spire ; and notwithstanding the similarity 

 of the shells he very judiciously separated them and form- 



