48 



VALVATA. 



Family VALVATIDAE. 



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

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

 the lateral lanceolate, hooked and denticulated. 

 Eostrum produced; tentacles cylindrical; the 

 eyes sessile at their external bases. Mantle sim- 

 ple 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 Avhirled ; 

 whirls with a thin elevated edge. Shell sjDiral, 

 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. — H. & A. Ad?^ 



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

 trate the animal of this family (fig. 83). 



Operculum of 

 V. tricarinatn, 

 greatly magni- 

 fied. 



VAI^VATA, 0. F. MiJLL. 



[Shell turbinate or discoidal, umbilicated, thin, 

 whirls round, simple or keeled, covered with a horny 

 epidermis ; apertui'e circular, peristome continuous. 

 The species of this small genus inhabit the ponds 

 and ditches of Europe and North America. When 

 the animal progresses, the delicate, retractile, bran- 

 chial plume is projected over the neck. The female 

 deposits her eggs in a single, coriaceous, spherical 



capsule, which is affixed to stones or the stems of aquatic plants. 



—H. & A. Ad.'] 



Vtilvata sin- 

 cera, greatly 

 mairnified. 



Valvata tricarinata, Say. — Shell witli three -volutions ; three 

 revolving, carinate, prominent lines, giving to the whirls a quadrate instead 

 of a cylindric appearance. Suture canaliculate, in consequence of the 

 whirls revolving below the second carina and leaving an interval. Spire 

 convex, apex obtuse. Umbilicus large. Carinse placed, one on the upper 

 edge of the whirl, one on the lower edge, and the third on the base beneath. 

 Breadth one-fifth of an inch. 



