VALVATIDiE. 343 



Fam. VALVATID.E. 



Lingual membrane with the teeth in seven series 

 (3*1 "3), the central teeth broad, with a hooked and den- 

 ticulated apex, the lateral lanceolate, hooked, and den- 

 ticulated. Rostrum 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-whorled, 

 whorls 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. 



Genus VALVATA, O. F. Miiller. 



Shell turbinate or discoidal, umbilicated, thin, whorls 

 round, simple or keeled, covered with a horny epidermis ; 

 aperture circular, peristome continuous. 



8yn. Valvearius, Dtim. Concinna, Hubn. 



Ex. V. cristata, Miiller, pi. 36, fig. 6. Operculum, V. 

 piscinalis, Miiller, fig. 6, a, 6, b. Shell, V. piscinalis, 

 fig. 6, c. V. (Tropidina) tricarinata, Lesueur, fig. 6, d. 



The species of this small genus inhabit the ponds and 

 ditches of Europe and North America. When the 

 animal progresses, the delicate, retractile branchial plume 

 is projected over the neck. The female deposits her eggs 



