ISO 



PERISTOMAD^. 



Shell conic or flat : aperture circular, with the mar- 

 gin united all round, and furnished with an oper- 

 culum. 



24. Valvata. || 25. Paludina. 



XXIV. VALVATA. 



Shell with the spire a little elevated, or flat and disk- 

 like : aperture quite circular, united all round, and 

 furnished with an horny operculum marked with 

 a single raised spiral line. 



114. Valvata ohtusa. Shell globular, with an ele- 

 vated obtuse spire, and a deep central umbilicus. 



Valvata obtusa. Brard, p. 190. t. 6.f. 17. 

 Cyclostoma obtusum. Drap. p. 33. t. 1./. 14. 

 Turbo fontinalis. Mo7if. p. 348. t. 22. /. 4. 

 Turbo thermalis. Dillwyn, p, 852. 



