32 LIMNEA DESIDIOSA. 



form irregular facets: spire about as long as 

 the aperture, and rapidly attenuated to an 

 acute point: there are five convex whirls, sepa- 

 rated by a deep suture: body whirl much the 

 largest: aperture wide, generally obtuse poste- 

 riorly; peristome nearly level: labium thick and 

 not appressed anteriorly: columellar fold slight, 

 or wanting. 



Color light ochraceous, sometimes brownish: 

 polished within; and occasionally white na- 

 creous, or pink, anteriorly. 



Geographical Distribution. From latitude 

 35° to 45°, and from New England inclusive to 

 the Mississippi; inhabiting rivulets and small 

 lakes in great abundance. 



OBSERVATIONS. 



This species is subject to great variation in 

 the form of the shell, but the animals of the 

 slender and the ventricose varieties cannot be 

 distinguished; and the shells approach each 

 other by insensible gradations, as I have 

 ascertained from the examination of several 

 hundred specimens, many of them whilst living. 

 Those represented by figures 1, 4, 5, 6, 7, 8, 9, 

 arc from a pond of spring water twenty feet in 



