94 



LAND AND I'RESU-WATJaK ailKLLS OF N. A. [PART III. 



posterior base of tlie teiitacula ; base or foot of tlie animal dilated, oval, 

 obtuse before and beliind. 



Found under stones, &c., iu moist situations, on the margins of rivers. 

 Lilve those of tlie genera Lymnxa and Plunodus, this animal possesses the 

 faculty of crawling on the surface of the "water, in a reversed position, the 

 shell downward. (^Say.) 



Cyclostoma lapidaria, Say, Journ. A. N. S. Phila. I, 13 (1817) ; Binney's 



ed. 59. 

 Amnicola lapidaria, Haldeman, Mon. p. IS, pi. i, f. 10 (1844 ?) ; Jour. 



A. N. S. Phila. VIII, 200 (1842). 

 Paludina lapidaria, Say, Nich. Ency. 3d ed. (1819) ; Bixney's ed., p. 56. 



— KtTSTER in Chemn., ed. 2, p. 54, pi. x, f. 21, 22. — DeKay, N. Y. 



Moll. 8U (1843). 

 Melania lapidaria, Lewis, Bost. Proc. VIII, 255 ; Phila. Pr. 1862, 290 (no 



descr.). 

 Pomatiopsis lapidaria, Tryon, Proc. Phila. Acad. 1802, 452 (no descr.). 



This is a widely distributed species, ranging at least from 

 Georgia to New York, and from Missouri to Michigan. It is 

 also found in the postpleiocene of the Mississippi River bluffs. 



I have already given a figure of the animal and lingual den- 

 tition (Figs. 186 and 187). 



Pomatiopsis llistrica, Say. — Shell conic ; whirls slightly 



wrinkled, convex ; suture x^rofoundly indented ; aperture oval, nearly 



orbicular ; labrum with the superior edge not appressed to the 



Fig. 189. preceding whirl, but simply touching it ; umbilicus rather 



£\^ large, rounded. 



fcJ Length, less than one-tenth of an inch. Cabinet of the 



Academy. 



The smallest species I have seen. The aperture somewhat 

 resembles that of a Valvata, to which genus it may probably 

 be referable. Mr. Jessup obtained two specimens on the shore 

 of Cayuga Lake. (Say.) 



Paludina lustrica, Say, Jouru. A. N. S. Phila. II, 175 (1821) ; Bixxey's 



Pomati- 

 opsis 

 lustrica. 



