72 LAND AND FRESH-WATER SHELLS. 



9. Ancylus. Shell conical, oblong, limpet-shaped ; apex 

 pointed and bent to the right ; spire dextral or sinistral. Animal 

 with two cylindrical tentacles, with the eyes at their base ; foot 

 large. 



(a) Shell dextral, conoid, thin, yellowish-grey or horn-coloured ; 

 apex recurved ; mouth ovate. Height | to Jth inch. Streams and 

 rivulets. Common as far north as Aberdeen. A. fluviatilis^ 



(b) Shell sinistral, oblong, horn-colour tinged with yellow or 

 green, thin, glossy, compressed at the sides ; apex acute, sub- 

 central ; mouth somewhat oblong. Length | inch. Lakes? 

 ponds, canals, and sluggish .streams. Somewhat local. 



A. lacustris.^ 



(TERRESTRIAL.) 

 Family II. Limacidae. 



Shell placed under the mantle, granular or shield-like. Body 

 united in its whole length with the foot beneath, there being 

 no visceral hump ; tentacles four, cylindrical, the dorsal pair 

 bearing the eyes ; mantle shield-like. 



10. Arion. Shell consisting oi calcareous granules. Mantle 



Fig. 29. Arion atcr. 



38 v. cafuloides, elevated, very convex anteriority and laterally, nearly convex 

 behind, aperture oboval ; v. albida, milk-white, strke finer ; v. gibbosa, slightly 

 elevated, extremely convex, subgibbous in front, convex laterally, nearly straight 

 posteriorly, apex obtuse, aperture oboval ; v. costata, whitish or greyish, strire 

 well marked. 



39 v. albida, milk-white.; v. comfressa, rather larger and considerably broader 

 and flatter. 



