220 



stoma; A. meridionalis; A. costatus; A. albus; A. striatus; 

 A. Tinei; and A. Fabrei. Bourg. in Jour. Conch. 1853, 

 187. A. riparius. Desm. Bull. Soc. Philom. 1814, 19. t. 1. 

 f. 2. A. capuloides. Jan, in Risso, Mai. Com. 37. t. 1. 

 f. 7. A. deperditus. Dupuy, Hist. Moll. 494. t. 26. f. 4. 

 A. vitraceus, and A. striatus. Morclet, Moll. Port. 87. t. 8. 

 f. 3, 4. Ancilus fluviatilis, and sinuosus. Brard. Coq. Par. 

 200. t. 7. f. 3, 4. Ancylus sinuosus. Gras, Moll. Franc. 

 t. 5. f. 8. A. (Ancylastrum) fluviatilis. Moq. Tund. Moll. 

 Franc, ii. 484. t. 35. f. 538. t. 36. f. 149. 

 Var. 1., with slight longitudinal stria 1 . 



In streams and rivulets attached to stones. 



Animal greyish. 



Shell about a quarter of an inch in diameter, and 

 nearly as much in height, semi transparent, light 

 horn-colour, covered with a dusky green skin slightly 

 marked with concentric striae, inside bluish white, 

 glossy ; the crown slightly curved downwards. 



The shells of these animals are modified in form 

 and elevation according to the surface of the sub- 

 stance to which they may happen to be attached, as 

 in the marine Patella ; hence the Continental natu- 

 ralists have made them into several species depend- 

 ing on the elevation of the cone of the shell, the 

 more or less concave form of the different margins 

 of the aperture, the acuteness or bluntness of the 

 apex, and the strength of the radiating striae. 



4. VELLETIA. (Lake Limpet.) 



The animal like Ancylus, but dextral ; the shell 

 oblong, compressed, conical, with the apex rather 

 behind the middle, bent to the left, as in other 

 dextral shells ; mouth elongate ; orifices of re- 

 spiration, &c., on right side of mantle. 



