908 HELIX. 



Martini Beil. Mag. iv. p. 258. t. 8. f. 20. 



Inhabits stagnant water in Sweden, and other parts of Europe. 

 LinncEus. France. Geoffroy. Denmark. Muller. Ger- 

 many. Schroeter. England. Montagu. 



Shell about three-tenths of an inch in diameter, of a horn-co- 

 lour, and differs from H. Vortex, to which it is most nearly 

 allied, in being equally concave on both sides, and in the 

 want of a keel on the outer whirl. 



POLYGYRATA. 50. Shell coiicave above and flat be- 

 low, with ten rounded whirls, and the aper- 

 ture marginated. 



Helix polygyrata. Born Mus. p. S73. t. 14. f. 19 and 20. 



Chemnitz, ix. part 2. p. 98. t. 127. f. 1124 and 1125. 

 Helix polygyra. Gmelin, p. 3624. 

 Helix, No. 308. Schroeter Einl. iii. p. 266. 

 Shell about an inch and three-quarters in diameter, of a yellow- 

 ish colour, with ten rounded and obliquely striated whirls ; 

 aperture ovate, and marginated. 



coNTORTA. 51. Shell flattish above, and deeply 

 umbilicated below, with six whirls. 



Helix contorta. JLinnaus Syst. Nat. p. 1244. Chemnitz, 

 ix. part 2. p. 98. t. 12?. f. 1126. Gmelin, p. 3624. Do- 

 novan, iii. t. 99. Montagu Test. p. 457. t. 25. f. 6. Ma- 

 ton and Racket, in Lin. Trans, viii. p. 191. Dorset 

 Cat. p. 53. t. 20. f. 11. 

 Helix crassa. Da Costa Brit. Conch, p. QQ. t. 4. f. 11. 

 Helix umbilicata. Pulteney Dorset Cat. p. 47. 

 Helix, No. 314. Schroeter Einl.Vi. p. 267. 

 Planorbis contortus. Muller Verm. ii. p. 162. Schroeter 



Fluss. p. 243. t. 5. f. 29. 

 Le Planorbe k six spirales rondes. Geoffroy, p. 89. No. 3. 



t. 3. 

 Petiver Gaz. t. 92. f. 8. Martini Berl. Mag. iv. t. 8. 

 f. 21. 

 Inhabits stagnant waters in Sweden, and other parts of Europe. 

 Linnaus. England. Petiver. France. Geoffroy. Den- 

 mark. Muller. Germany. Schroeter. 

 Shell about two tenths of an inch in diameter, and the whirls 

 nearly one-tenth thick ; the colour is brown, reddish chest- 

 nut, or horn-colour, and when alive it is covered with a 

 dusky epidermis ; it has five or six M'hirls separated by a 

 small deep suture, and is distinguished from the other de- 



