226 HELICIDJB. 



varieties inhabit wet and dry localities indifferently ;" and 

 Malm has confirmed these observations and added that, 

 out of 100 specimens which he had collected in one 

 spot, twenty of them belonged to the variety. I have 

 not been so fortunate as to find them living together. 

 Miiller describes the present species as common in wet 

 moss, and the variety as very rare in an elevated spot at 

 some distance from any water. Some specimens, how- 

 ever, of the variety are more strongly ridged than others ; 

 and there is an evident transition from the smooth to the 

 ridged form. I cannot detect any difference between 

 the shells, except in respect of the membranaceous 

 ridges, which form part of the epidermis and are easily 

 rubbed off, leaving the surface of the shell quite smooth. 

 This species is common in our upper tertiary deposits. 

 Abroad it ranges from Siberia (according to Gerstfeldt) 

 to Lugano (according to Stabile), as well as to Corsica 

 and even to Madeira and the Azores. Gould says that 

 the typical form is rather common near Boston, and 

 that it has been noticed on the Ohio, and on the banks 

 of the Missouri, as high up as Council Bluffs. With 

 reference to the opinion of some that it had been intro- 

 duced into America from Europe, Dr. Binney remarks 

 that " it does not seem possible that so small an animal, 

 if naturalized since the arrival of Europeans, could have 

 been able to penetrate to the remote points in the 

 interior of the Continent where it is now found." With- 

 out quite concurring with the American conchologist in 

 this remark, I do not see how this little snail is likely to 

 have been transported across the Atlantic from the one 

 hemisphere to the other. It only inhabits waste and un- 

 cultivated spots ; and a flower- or kitchen-garden would 

 be the last place to look for it. But the modes of trans- 

 port are various ; and it would be rash to assert positively 



