BULLA. 489 



Helix achatina. Gtnelin, p. 3665. 



Helix, No. 240. Schroeter Einl. i. p. 245, &c. 



Lister Conch, t. 1059. f. 5. Petiver Gaz. t. 10. f. 8. 

 Schroeter Fluss. t. 6. f. 9, and f. 15. a and b. 

 Inhabits ponds and ditches in Great Britain, and many other 



parts of Europe. 

 This species a good deal resembles B.fontinalis, but is more 



glossy and of a darker colour, has a produced taper spire, 



and the aperture is shorter and more contracted. Gmelin's 



Helix achatina appears to differ from his H. marmorata, 



only in being a younger shell. 



gelatinosa. 40. Shell ventricose, very brittle, 

 pellucid, with the whirls reversed ; spire ob- 

 solete ; aperture ending in a beak. 



Bulla gelatinosa. Gmelin, p. 3428. 



Planorbis gelatinus. Muller Verm. ii. p. 170. Schroeter 

 Fluss. p. 293. 



Inhabits the rivers of Denmark, but is very rare. Muller. 



Shell two and a half lines long, ventricose, tawny, diaphanous, 

 shining, extremely slender and brittle, and as light as a fea- 

 ther ; the first whirl is very large, the others obsolete and 

 depressed so as to form a broad blunt summit ; the aperture 

 ends in a long and very sharp point. Inhabitant grey, thrice 

 as large as the shell which it completely envelopes in a thick 

 gelatinous membrane. 



terebellum. 41. Shell cylindrical, with a subu- 

 late spire ; and the base truncated. 



Bulla Terebellum. Lin. Syst. Nat. p. 1185. Martini, 

 ii. p. 191. t. 51. f. 568 and 569. Chemnitz, x. p. 124. 

 t. 146. f. 1362 and 1363. Born Mus. p. 206. Schroe- 

 ter Einl. i. p. 168, and Inn Bau Conch, p. 15. t. 2. f. 3. 

 Gmelin, p. 3428. Schreibers Conch, i. p. 91. 



Terebellum subulatum. Lamarck Syst. des Anim. p. 72, 

 and Ann. du Mus. xvi. p. 301. 



La Tariere. Favanne, ii. p. 805. t. 19. f- D. 



Bonanni Rec. and Kirch. 3. f. 57. Lister Conch, t. 736. 

 f. SO and 31, and t. 737. f. 32. Rumphius, t. 30. f. S. 

 Pet. Amb. t. 13. f. 24. Gualter, t. 23. f. O. Argen- 

 ville, t. 1 1. f. G. Klein Ost. t. 2. f. 48 and 49. Knorr, 

 ii. t. 4. f. 4 and 5. Enc. Meth. t. 360. f. \.a, b, and c. 

 Inhabits Amboyna. Rumphius. Mindanao, and the Isle of 



France. Favanne. 



