36 VALVATID^E. 



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. b. 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.l0.f. 115.) 



Valvata cristata. Gray, Man. 98; MiUler, Verm. 198. ; Alder, 

 Mag. Zool. and Pot. ii. 116. ; Forbes and Hanley, B.M. iii. 

 20. t. 71. f. 11. 12, 13. Valvata spirorbis. Drop. 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. Gmel. 3675. Helix cristata. Mont. p. 46. ; 

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

 69. Trochus cristatus. Maton and Racket, Linn. Trans. 

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

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

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

 Coxe's Trav. iii. 436. Valvata branchialis. Gruithuuen, 

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

 vata minuta. Drop. 42. t. 1. f. 3638. ; Turlon, 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. 



