VALVATA. 35 



each side ; the apical denticules larger than the rest. 

 (Fig. 7.) 



Nerita piscinalis. Mutter, 172. Trochus cristatus. Schroet, 

 Fluss-conch. 280, t. 6. f. 11. Valvata obtusa. Brard, p. 

 190. t. 6. f. 17.; Turton, Man. ed. 1. 130.; Pfeiffer, 198. t. 

 4. f. 32. t. 1. f. 13. Yalvata fontinalis. Leach, Syn. Moll 

 206. Turbo cristata. Poir. Prod. 29. Nerita obtusa. 

 Studer, Coxe's Travels, iii. 436. Cyclostoma obtusum. 

 Drap. p. 33. t. 1. f. 14. Turbo fontinalis. Mont. p. 348. 

 t. 22. f. 4. Turbo thermalis. Dillwyn, p f 852. Helix 

 piscinalis. Gmel. 3627. Valvata piscinalis. Lam. vi. 172. ; 

 Kenyon, Mag. N. Hist. iii. 425. f. b. c. d. ; Alder, Mag. 

 ZooL and Bot. ii. 116. Lymnea fontinalis. Flem., Ed. 

 Ency. vii. 78. Nerita pusilla. Mutter, Verm. 171. 



Young rather depressed, umbilicus rather wider. Helix 

 fascicularis. Gmelin, S. N. 3641.; Alien Syst. 74. t. 8. f. 16. 

 Valvata depressa. Pfeiffer, D. Moll. J. 100. t. 4 f. 33. Val- 

 vata minute. Drap. Hist. Moll. 42. t. 1. f. 36. 38. Val- 

 vata Moquiniana. Dupuy, Moll. Franc. 586. t. 28. f. 15. 



In canals and ponds; common to all parts of 

 England. 



Animal whitish ; trunk grey, rugose. 



Shell nearly a quarter of an inch long and as much 

 broad, globular, thin, light horn-colour, very finely 

 spiral-striate, and marked with some obscure con- 

 centric lines; spire of four volutions, tumid, and 

 deeply defined, and having much the appearance of 

 a Trochus, with a deep central umbilicus ; opercu- 

 lum dull greyish white. 



Varieties: 1. Shell high, um- Fi 9- 8 - 



bilical; cavity small. 2. Shell de- 

 pressed, umbilicus deep ; also varying 

 much in size, some specimens being 

 three or four times as large in the 

 adult age as others. 



Some continental naturalists, overlooking the fact 



D 2 



