80 HELICIDJE. 



Var. I. bigranata. Smaller, thicker, with two 

 denticles. 



Var. II. albina. White. 



Genus VII. VERTIGO. 



The members of this genus have only two tentacles, 

 while those of the preceding genus have four. In 

 order to aid the collector to identify these minute and 

 very puzzling little shells, I have tabulated some of 

 the most important differences of those which are 

 dextral and furnished with teeth. (See Appendix B.) 



The ten species have been conveniently arranged as 

 follows : 



A. dextral, denticulated. ANTIVERTIGO, LiLLJE- 

 BORGII, MOULINSIANA, PYGM^A, ALPESTRIS, SUB- 

 STRIATA. 



B. sinistral. PUSILLA, ANGUSTIOR. 



C. dextral, without teeth. EDENTULA, MINUTIS- 

 SIMA. 



A. DEXTRAL, denticulate. 



1. Y. ANTIYERTIGO (not reversed). 



Oval, thin, semi-transparent, glossy, rufous horn- colour; 

 whorls four and a half, tumid ; spire short, abrupt ; mouth 

 semi- oval, contracted in the middle of the outer edge ; 



