VALVATA. 
35 
each side ; the apical denticules larger than the rest. 
(Fig. 7.) 
Nerita pisclnalis. Muller^ 172 . — ■ Troclms cristatus. Schroet., 
Fluss-conch. 280, t. 6. f. 11. — Valvata obtusa. Brard.,\i. 
190. t. 6. f. 17.; Turton., Man. ed. 1. 130.; Pfeiffer^ 198. t. 
4. f. 32. t. 1. f. 13. — Valvata fontlnalis. Leach., Syn. Moll. 
206. — Turbo cristata. Poir. Prod. 29. — Xerita obtusa. 
Sluder., 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. Billwyn., p. 852. — Helix 
piscinalis. 3627. — Valvata piscinalis. Lam. vi. 172. ; 
Kenyon., Mag. N. Hist. iii. 425. f. h. c. d . ; Alder., Mag. 
Zool. and Hot. ii. 116. — Lymnea fontinalis. Flem.., Ed. 
Ency. vii. 78. — Nerita pusilla. Muller., 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 minuta. 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- 
bilical ; cavity small. 2. Shell de- a 
press^ed, 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 
Fig. 8. 
