86 THE LAtfl) AtfD FRESHWATER ItOLLUSCA OF DORSETSHIRE. 



FAMILY HI. VALVATID.&. 



VALVATA, Miiller. 

 1. VALVATA PTSCINALIS, Midler, pi. 6. 



TURBO FONTINALIS, Pult. cat., p. 45, Rack, ed., p. 50, pi. 18, 



f. 3,4. 



Body yellowish grey, with small and indistinct milk-white specks. 



Shell globular, conical above, solid, and opaque, brownish yellow, 

 the surface ridged with longitudinal striae, spire a reddish" hue, 

 whorls five, the last forming about half of the shell, divided by a 

 deep suture ; mouth circular and expanded. The inner lip forms 

 with the outer Up a complete peristome ; umbilicus very deep, 

 exposing the interior of the spire ; operculum somewhat depressed, 

 the outer edges slightly overlap one another. L.0.25. B.0.275. 



Hab. Canals, ponds, ditches, and slow rivers. River Frome, 

 Wareham ; river, Chamberlayne's, Bere Regis -, watercourses, 

 Sturminster Marshall ; abundant. It occurs in the Quaternary 

 tufaceous deposit at Blashenwell, Kingston, Purbeck (J.C.M.P.). 



2. v. CRISTATA, Muller, pi. 6. 



Body dark grey or brown, slate-colour underneath. 



Shell depressed, resembling Planorbis; flattened above, very con- 

 cave below, surface with well marked longitudinal striae, fragile, 

 horn-colour, slightly transparent; whorls from three to four, the last 

 reaching the plane of the summit; mouth large, circular; suture 

 deep ; umbilicus large and open, showing the interior of the spire ; 

 operculum circular, concave ; the edges of each whorl, of which there 

 are about twelve, form slight ridges. L.0.025. B.0.125. 



Hab. Similar to that of V. p'ncitialis. River Frome, Red- 

 clifT, near Wareham ; Stour Spettisbury ; The Lidden, near 

 Sturminster Newton -, Chamberlayne's, Bere Regis. Quaternary 

 tufaceous deposit at Blashenwell, Kingston, Purbeck (J.C.M.P.). 



