] 76 HELICID^. 



those shells by the front of the last whorl being 

 convex and simple, and not flattened and furnished 

 with a keeled ridge near the outer edge, as is the 

 case with the young of all the species of that genus. 



From Bulimus and Pupa this genus is distinguished 

 by the aperture being left-handed ; from Clansilia, in 

 having the ultimate volution proportionately larger 

 than the next ; and from Vertigo, in the regularity 

 of its mouth. 



Draparnaud erroneously describes this shell as 

 having a clausium. (See Ferussac, Essai, iii.) 



82, 1. Bale A perversa. Fragile Moss Shell. — 



Shell rather linear-oval, transparent yellowish ; 



whorls six or seven ; mouth subquadrate. (t. 6. 



f. 70.) 



Turbo perversus. Linn. S. N. 1240.; Mont. p. 335. t. 11. 

 f. 12., Supp. 131. — Pupa fragilis. Drap. Hist. p. 68. t. 4. 

 f. 4. — Clausilia fragilis. Feruss. Essai, 51.; Studer; Jef- 

 freys, Linn. Trans, xvi. 351. — Balaea fragilis. Leach, Moll. 

 p. 116.; Alder, Cat. 8. 427.; Mag. Zool. and Bot. ii. HI.; 

 Forbes and Haul ey, B. M.'iy. 114 t. 128. f. 8, 9. — Balea 

 fragilis. Gray, Zool. Journ. i. p. 61.; Rossm. Icon. x. f. 638. 

 — Balea perversa. Leach, Syn. Moll. 83. ; Flem. B. A. 271. 

 — Clausilia uniplicata. Culcara, 82. — Odostomia perversa. 

 Flem. Ed. E»cy. vii. 76. — Pupa perversa. 3Ioq. Tand 

 Moll. F. ii. 349. t. 25. f. 6. 14. — Bulimus perversus. Poiret, 

 Prod. 57. — Clausilia parvula. Gart. Conch. Wett. 22. — 

 — Clausilia perversa. Charpent. — Fusulus fragilis. Fitz. 

 Syst. 108. — Stomodonta fragilis. Merrneft, Moll. Pyr. 43. 



On the trunks of trees, under the bark, and em- 

 bedded in the lichen ; also in the fissures of rocks. 



Animal brownish yellow ; neck black ; foot grey, 

 granular, spotted, narrow, and elongate ; tentacles — 

 upper thick, short, clavate, — lower scarcely visible, 

 very small, tubercular ; muzzle very blunt and large. 



