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 5 to ^th inch. Streams and 

 rivulets. Common as far north as Aberdeen. A. fliiviatilis}'^ 



(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. lacustrisP 



(Terrestrial.) 

 Family II. — Limacidse. 



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 ot calcareous granules. Mantle 



"^ V. capitloides, elevated, very convex anteriorily and laterally, nearly convex 

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

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

 posteriorly, apex obtuse, aperture oboval ; v. cosfafa, whitish or greyish, stria; 

 well marked. 



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

 ?.nd flatter. 



