VALVATA. 35 



each side ; the apical denticules larger than the rest. 



(Fig. 7.) 



Nerita piscinalis. Miiller, 172. — Trochiis cristatus. Schroet, 

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

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

 4. f, 32. t. 1. f. 13. — Valvata fontlnalis. Leach, Sijn. Moll. 

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

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

 Drop. p. 33. t. l.f. 14. — Turbo fontinalis. Mont. p. 348. 

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

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

 Kenyan, Mng. N. Hint. iii. 425. f. b. c d. ; Alder, Mag. 

 Zool. and Bot. ii. 116. — Lymnea fontinalis. Flem., LJd. 

 Ency. yu.7S. — Nerita pusilla. Midler, Verm. 171. 



Young rather depressed, umbilicus rather wider. — Helix 

 foscicularis. Gmelin, S. N. 3641.; Alten Si/st. 74. t. 8. f. 16. — 

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

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

 vata Moquinlana. 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 hio;h, um- Fig.s. 



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 facA 



D 2 



