VERTIGO. 157 



glossy ; whorls compact, gradually increasing ; spire short, 

 sometimes sinistral ; mouth usually provided with teeth, or 

 folds, which are placed considerably within the aperture, and 

 its outer lip is then contracted ; umbilicus minute. 



These tiny snails resemble the Ptipce in many re- 

 spects, but differ from them essentially in being desti- 

 tute of the lower pair of tentacles, a fact which was 

 first noticed by M tiller, who consequently instituted 

 the present genus. 



Some species are semi-aquatic. 



A. Shell oval or ovate ; spire dextral ; mouth 

 provided v/ith teeth. 



I. Vertigo anttverti'go,* Draparnaud. Pl. IX. 



Body short, thick, greyish-black, faintly tinged with slate- 

 colour, tubercles very minute, more or less black ; tentacles 

 black, rather near together at their base, bulbs oval, forming 

 about a third of the tentacles ; foot oblong, narrow, margins 

 pale grey, with minute black specks ; sole of a uniform slaty- 

 grey. 



Shell ovate, thin, semitransparent, glossy, of a chestnut- 

 brown colour, with exceedingly fine close-set striae in the line 

 of growth, and very indistinctly striate spirally ; periphery 

 rounded ; epidermis very thin ; whorls 4I-, ventricose, abruptly 

 increasing, body whorl occupying about half of the shell ; spire 

 short, apex obtuse ; suture deep ; mouth approaching to semi- 

 oval, but the centre of the outer edge is considerably contracted, 

 causing the aperture to appear somewhat angular, usually pro- 

 vided with the following teeth, which in colour resemble the 

 rest of the shell, and are irregular in shape and size ; two or 

 three on the base of the penultimate whorl, two of them rather 

 strong and pointing towards the outer edge ; the third or inner 

 one, when present, much smaller, one or two on the pillar, and 



* Not reversed. 



