457 



it has as frequently occurred to us ; fometimes in the 

 fame pools with the Vortex, and at other times in 

 feparate places. 



64. 

 Helix contorta. Lin. Syjl. p. 1244. Contort a. 



Gmel. Syjt. p. 3624. 37. 



C/iem. Conch, ix. t. 127. 'f. 1126. 



Petiv. Gaz. t. 92. f. 8. 



Turt. Lin. iv. p. 511. 



Schroeter Flujfconcji. p. 243. t. 5. f. 29. 



Don Br. Shells, iii. t. 99. 

 Planorbis contortus. Midler Verm. ii. p. 162. No. 348. 

 Helix craffa. Da Cofta p 66. t. 4. f. 11. 



Helix umbilicatus. Pult. Cat. Dorfet, p. 47. 



H. with a deprefled, fub-pellucid, brown, horn-co- 

 loured fhell ; fometimes rufous, or chefnut, and not un- 

 frequently covered with a dufky epidermis when alive: 

 dead fhells become white. It has five or fix volutions 

 placed lateral; the outer one rounded, not carinated; 

 thefe all rife on the upper part almofl to an edge, being- 

 very clofe together, with only a very (mall, but deep 

 deprefled line between; in the centre a Jub-umbilicus : 

 the bafe, or under part, is largely and deeply umbilicated, 

 [hewing every volution, fpirally defcending to the bot- 

 tom in a very elegant manner : aperture arcuated, by 

 clafping the body whirl. Diameter two-tenths of an 

 inch, and not quite one tenth thick, 



Nnn Da Costa 



