8 land and fresh- water shells of n. a. [part iii. 



Fossil Species. 

 Ampullaria ? perovata, Conkad, Proc. Acad. Nat. Sc. Pliilad. Ill, 21, pi. i, 



Family VALVATIDAE. 



Lingual membrane witli teeth in seven series (3, 1, 3); 

 the central teetli broad, with a hooked and denticulated apex, 



Fig. 9. 



Lingual dentition of Valvata triearinata. 



Fig. 10. 



the lateral lanceolate, hooked and denticulated. Eostrum 



produced; tentacles cylindrical; the eyes sessile 



at their external bases. Mantle simple in front; 



gill plumose, exposed, the lamina pinnate, spirally 



twisted, protected by a long, slender respiratory 



lobe. Foot bilobed in front. Operculum horny, 



orbicular, spiral, many whirled; whirls with a 



thin elevated edge. Shell spiral, turbinate or 



discoidal, covered with an epidermis; aperture 



with the peritreme entire. 



The species of this family are distributed throughout the 



temperate regions of the globe, living in slow running rivers, 



ditches, and lakes. 



I have copied Haldeman's figure of ValvcUa sincera to illus- 

 trate the animal of this family (fig. 11). 



Operculum of 

 V. triearinata, 

 greatly magni- 

 fied. 



VAI.VATA, 0. F. MiJLL. 



Shell turbinate or discoidal, umbilicated, thin, 

 whirls round, simple or keeled, covered with a liorny 

 epidermis ; aperture circular, peristome continuous. 



The species of this small genus inhabit the ponds 

 and ditches of Europe and Xorth America. When 

 the animal progresses, the delicate, retractile, bran- 

 chial plume is projected over the neck. The female 



