18 PALUDINTD.E. 



This shell is much rarer than the last, and appears to be 

 confined to the sonth of England. It inhabits many 

 localities in the region of the Thames, and its tribntaries. 

 Bath (Clark); Bristol, Olnmber Lake, Cardiff (Jeffreys). 

 Rare near Scarborough (Bean). It is said to occur near 

 Preston in Lancashire (Kenyon). 



Mr. Jeffreys observes, " that individuals resembling the 

 elongated variety in Turton's collection, which that author 

 had supposed identical with the Cycl. viride of Draparnaud, 

 are met with in Greenwich marshes." 



VALVATA, 0. F. Muller. 



Shell turbinated or discoid, thin, umbilicated, whorls 

 much rounded, smooth, carinated or striated, covered with 

 a corneous epidermis : mouth circular, peristome continu- 

 ous ; operculum horny, concentrically spiral. 



Animal with a produced muzzle; its head furnished 

 with long, cylindric tentacles, bearing sessile eyes beside 

 their external bases ; foot bilobed in front ; branchial 

 plume long, pectinated, partially exserted. Lingual arma- 

 ture of series of denticles, each composed of a central broad 

 tooth with a hooked and denticulated summit, and three 

 lanceolate denticulated hooked laterals. 



This genus is of more ancient origin than is usually 

 assigned to it. We have found unquestionable species 

 in the freshwater beds of the oolitic period. At present 

 it is distributed through the temperate regions of the 

 earth, living in slow running rivers, ditches, and lakes, but 

 presenting no great variety of shape or ornament, and but 

 few specific forms. 



