114 BRITISH MOLLUSKS. 



Vertigo striata. (Considerably enlarged.) 



Genus XII. VERTIGO, Milller. 



Animal ; body rather short, acuminated towards the tail, carrying a 

 blunt tumidly whorled shell, mostly dusky grey, pale towards 

 the sides ; upper tentacles rather short, no lower tentacles. 



Shell; minute, sometimes sinistral, cylindrical, variously umbili- 

 cated, composed of from four to six semitransparent whorls, 

 mostly smooth, rather obtuse at the apex, rounded at the base ; 

 aperture ovate, generally more or less toothed within, the 

 teeth having a parietal form, winding in thread-like ridges 

 into the interior., 



The absence of lower tentacles is not the only character in which 

 Vertigo differs from Pupa. The species are all minute, the largest 

 Vertigo being smaller than the smallest Pupa; and they are cha- 

 racterized by the distinct habit of living in more watery places, 

 generally about the roots of grass at the sides of lakes and rivers, 

 though occasionally at a considerable elevation on the hills. The 

 proportion in the number of species of Vertigo to Pupa in all parts 

 of the world, so far as they have been eliminated from that genus, 

 is about seventy to one hundred and fifty ; but in Britain, we have 

 nine species of Vertigo to only four of Pupa. 



Our commonest and most widely distributed Vertigo is V. pygmcea. 

 It is abundant throughout our islands, and throughout Europe, 

 reaching to the Azores ; it is, moreover, the only British species 

 which has an extra-European range, passing into Siberia. Two 

 species, V. striata and edentula, are found throughout Britain, but 

 on the Continent they are confined chiefly to the central parts. 

 V. antivertigo appears throughout the Continent, and in England 

 and Ireland, but not in Scotland ; while V. minuta, which appears 

 nearly throughoiit Europe, is scattered and rare in Britain. V.pusilla, 

 which is peculiar to Northern and Central Europe, is found in Eng- 



