NEW SPECIES OF SHELLS. 13 



Description of Seven Species of American Fresh Water 

 and Land Shells^ not noticed in the systems. By Tho- 

 mas Say, 



Genus CYCLOSTOMA. 



A subdiscoidal or conic univalve. The aperture orbi- 

 cular, with a circularly continued margin, often suddenly 

 and widely reflected. 



SPECIES. 



C. tricarinata. Shell with three volutions; three re- 

 volving, carinate, prominent lines, giving to the whorls a 

 quadrate, instead of a cylindric appearance. Suture cana- 

 liculate, in consequence of the whorls revolving below the 

 second carina and leaving an interval. Spire convex, apex 

 obtuse. Umbilicus large. Carina placed, one on the up- 

 per edge of the whorl, one on the lower edge, and the 

 third on the base beneath. Breadth one- fifth of an inch. 



Inhabits the river Delaware. Rare. 



Found by Mr. Le Sueur, whose proposed name is 

 here adopted. 



C. lapidaria. Shell turreted, subumbilicate, with six 

 volutions, which are obsoletely wrinkled across. Suture 

 impressed. Aperture longitudinally ovate-orbicular, oper- 

 culated, rather more than one-third of the length of the 

 shell. 



Length about one-fifth of an inch. 



Collection of the Academy of Natural Sciences, 



Inhabitant not so long as the shell, pale; head elon- 

 gated into a rostrum as long as the tentacula, and emar- 

 ginate at tip; tentacula two, filiform, acuminated at tip, 

 short; eyes prominent, situated at the external or poste- 



