50 VALVATA. 



end ; filament rather short, translucent with longitudinal white 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 hicarinata is more conical and without so sudden an enlargement at 

 the end. The color of the hicarinata 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 hicarinata 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 

 hicarinata 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 hicarinata is quite light colored beneath, and rather a 

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

 above the periphery of the whirl, between which and the superior carina 

 it is quite dark. The supei'ior carina is large and erect, the inferior one 

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

 strise 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 

 apple green, globose object, passing from under the aperture of the shell. 

 This was shortly followed by others, and soon a transparent gelatinous 

 mass became visible. This mass was passed slowly over the right side 

 of the neck, under the pectiniform movable branchiae, until entirely dis- 

 charged against the perpendicular side of the vessel in which it was kept, 

 and there the mass remained attached, the parent having abandoned it 

 immediately. The time was fifteen minutes from the first appearance of 

 the mass until it was fairly discharged. The green globules were the ova, 

 of which I counted thirty in the transparent, globose gelatinous mass, which 

 was not more in diameter than one-twentieth of an inch, the transverse 

 diameter of the shell being about four-twentieths of an inch. In other 

 cases, I found the number of ova to differ ; some masses having only ten 

 or twelve. 



On the 23d, (eight days after), the ova were so far advanced as to be 

 changed to a dull faded green, the mass enveloping them having changed 

 by degrees in transparency, and becoming of a slightly ferruginous color. 

 As yet, no change of bulk or arrangement was observed. 



