10 LAND AND FRESH- WATER SHELLS OF N. A. [PART III 



tioned in the synonymy. The original descriptions and fac-similes 

 of the original figures now follow. 



Valvata bicarinata, Lea. — Shell orbicular, flattened above, bicariuate, 

 rather thick, horn-colored above, whitish below, widely umbilicate ; su- 

 tures impressed ; spire depressed ; whirls four, convex ; aperture rounded, 

 whitish within. 



Body rather short and white, head large, tapering, slightly enlarged at 

 the anterior termination, with a black mark passing 

 Fig. 14. from the neck between the eyes, tapering ofl" and 



reaching nearly to the end of the snout, where there 

 are two oblique black marks bordered in front by 

 white, and accompanied behind by several irregular 

 white spots, the anterior ones being the larger. 

 Valvata bicarinata. Branchia translucent, superior portion blackish, bor- 

 dered with white spots and occasionally obtruded ; 

 eyes round and deep black, placed at the posterior base of the tentacula, 

 surrounded by a white area ; tentacula long, rather tapering, obtuse at the 

 end ; filament rather short, translucent with longitudinal wjiite lines ; foot 

 wide and furcate anteriorly, where minute white spots may be observed. 

 Operculum thin, semitransparent, light horn color, increment circular and 

 rather coarse. 



Schuylkill River, west side, below Permanent Bridge. H. C. Lea. My 

 cabinet. Diam. .30, length .12 inch. 



In the form of the shell, this species closely resembles the tricarinata, 

 Say. It differs in having but two carinse, in having a wider umbilicus, 

 and the spire is more depressed. The animals of the two species differ in 

 form and color more than the shells. 



The head of the tricarinata is more cylindrical and enlarged at the ter- 

 mination, where it somewhat resembles the snout of the hog, while that 

 of the bicarinata is more conical and without so sudden an enlargement at 

 the end. The color of the bicarinata is lighter. In the black markings 

 they also differ. In the tricarinata there is a single blotch anterior to the 

 area between the eyes. In the bicarinata this extends also behind this 

 area ; and in addition may be observed two quite black marks above the 

 mouth, which the tricarinata does not seem to have. The tentacula of the 

 bicarinata are larger and more filiform. When in motion, the anterior por- 

 tions of the lobes of the foot are pointed, and recurved or hooked. 



The shell of the bicarinata is quite light colored beneath, and rather a 

 dark horn color above, the change of color taking place a short distance 

 above the periphe^ of the whirl, between which and the superior carina 

 it is quite dark. The superior carina is large and erect, the inferior one 

 is smaller. All the whirls are visible beneath. Very minute longitudinal 

 striae cover the whole surface. 



Having several living specimens of both these species, I observed them 

 closely with a lens while under water in a glass vessel. On the 15th of 

 May, while I had a tricarinata at the focus of my lens, I observed a small 



