158 LAND AND FRESH-WATER MOLLUSKS. 
escape notice. The animal is sluggish, and is 
not frequently to be seen stirring about. 
Genus Vertigo (Whorl Snails). 
The animal differs from that of Pupa in being 
destitute of the lower pair of tentacles. The 
shell is minute, sometimes sinistral; the peri¬ 
stome is thinner than in Pupa. Of the nine 
species inhabiting this country, V. Moulinsiana 
is the only one not known in a fossilized state. 
The species may be distinguished as follows :— 
1 . 
2 . 
3. 
4. 
5. 
Shell dextral ... 
Shell sinistral. 
Aperture edentulous 
Aperture toothed . 
2 
8 
3 
4 
Shell small, slightly striated ... 
Shell minute, strongly striated 
V. edentula 
V. minutissima 
Shell oval. 5 
Shell cylindrical . 7 
Aperture 4-toothed. 6 
Aperture with many teeth, aperture contracted,— 
V. antivertigo 
r. ( Shell small . V. pygmcea 
* ( Shell large . V. Moulinsiana 
( Shell subcylindrical, 4-toothed .. V. alpestris 
7. < Shell inclined to fusiform, strongly striated,— 
( V. substriata 
( Aperture subquadrate, six to seven teeth,— V. pusilla 
8. < Aperture triangular, contracted, four to six teeth,— 
( V. angustior 
