TURBO. 883 



are more or less produced on the marginal keel into short 

 spines. It has the general habit of the depressed Helices, 

 but the aperture is round, or sometimes rather oval, and the 

 latter variety was considered by Walker and Adams to be a 

 distinct species. 



CRisTATUS. 101. Shell flattish above, and imibili- 

 cated beneath, with three or four rounded 

 whirls. 



Turbo cristatus. Maton and Racket, in Lin. Trans, viii. 



p. 169. 

 Valvata cristata. Muller Verm. ii. p. 198. Schroeter Fluss, 



p. 240. t. 5. f. 26. a and b. 

 Nerita valvata. Gmelin, p. 3675. 



Helix cristata. Montagu Test. p. 460. Vign. 1. f. 7 and 8. 

 Le Porte Plumet. Geoffroy, p. 115. t. 3. 

 Helix. Walkers Minute Shells, f. 18. 

 Inhabits marshy places in Denmark. Muller. Pools of water, 

 and small streams about Paris. Geoffroy. In the Avon, and 

 ditches near Wedhampton, Wilts. Montagu. 

 Shell about one-tenth of an inch in diameter, sub-pellucid, of a 

 pale horn-colour, and composed of three, or sometimes of 

 four whirls, which are slightly wrinkled transversely, and 

 flattened at the summit ; the aperture is perfectly orbicular, 

 and is attached to, but not interrupted by, the body-whirl. 

 Muller, on account of the singular structure of the animal, 

 (which is well described in the Testacea Britannica by Mr. 

 Montagu) has placed this species in a separate genus, to 

 which he has given the name of Valvata. 



DEPRESSUS. 162. Shell mmute, depressed, with 

 four slightly wrinkled whirls, and umbilicat- 

 ed beneath. 



Turbo depressus. Maton and Racket, in Lin. Trans, viii. 



p. 170. 

 Helix depressa. Montagu Test. p. 439- t. 13. f. 5. 

 Inhabits the sea on the coasts of Cornwall and Devon. Mon- 

 tagu. 

 Shell scarcely one line in diameter, and of a pale brown colour; 

 Mr. Montagu says it resembles T. cristatus, but is much 

 smaller, stronger, and more opake, and has the apex rather 

 more prominent. 



