36 VALVATID^. 



that all conoid shells are more depressed in their 

 young state, have, from the peculiarity of their forma- 

 tion, regarded the young as a distinct species under 

 the name of Valvata depressa. (See f. 8. a. h. c.) 



The animal and operculum are well described by 

 Montagu [Test Brit, 351.), who justly compared 

 the animal to that of the next species, though in his 

 arrangement one shell is a Turbo and the other a 

 Helix; but he saw the difficulty of this arrange- 

 ment. See his note at p. 367., and also at p. 461., 

 where he describes the animal of V. cristata. 



8. 2. Valvata cristata. Crested Valve Shell. — Shell 

 discoid, flat above, and umbilicate beneath ; 

 whorls 3. (t. 10. f. 115.) 



Valvata cristata. Gray, Man. 98; Midler^ Verm. 198. ; Alder, 

 Mag. Zool. and Bot. ii. 110.; Forbes and Hanley, B.M. iii. 

 20. t. 71. f. 11. 12, 13. — Valvata spirorbis. Draji. p. 41. t. 

 1. f. 32, 33. ; Brard, p. 187. t. 6. f. 15, 16. ; Turton, Man.ed. 

 1. 131. f. 115. — Valvata Mulleri. Leach, Syn. Moll. 205. 

 Nerita valvata. Grnel. 3675. — Helix cristata. Munt. p. 46. ; 

 Vign. 1. f. 7, 8. — Planorbis cristatus. Flem. Ed. Ency. vii. 

 69. — Troclms cristatus. Maton and Backet., Linn. Trans. 

 viii. 167.— Turbo cristatus. Turton, Diet. p. 227.— Valvata 

 planorbis. Moll. 42. ; Drup. Tab. 41. t. 1. f. 34, 35.; Tur- 

 ton, Man. ed. 1. 132. f. 116. (?) — Valvata pulchella. Sfuder, 

 Coxe's Trav. iii. 436. — Valvata brancbialis. Gi-uithuisen, 

 Nov. Act. Nat. Cur. x. 1821, 437. t. 38. f. 13. — Junior. Val- 

 vata minuta. Drap. 42. t. 1. f. 36—38. ; Turton, Man. ed. 1. 

 f. 117. 



In ditches and canals, on aquatic plants. 



Shell about the tenth of an inch in diameter, pale 

 horn-colour, striate transversely, with three volu- 

 tions ; the upper surface a little sunk, the under side 

 umbilicate, so as to expose the interior volutions. 



