2 VALVATA. 



proceeds from the right side of the neck: anus 

 upon the right side. 



SHELL conoid or subdiscoid, umbilicated: 

 volutions cylindrical or subcylindrical; aperture 

 circular, not modified by the penultimate whirl; 

 closed with an orbicular opercle, whose lines of 

 growth are concentric. 



EXAMPLE. V. tricarinata, Say. 



HABITS. Found upon the muddy bottom of 

 quiet and not very shallow waters. The ova 

 are deposited in detached greenish globules, 

 each containing a number of germs. 



OBSERVATIONS. 



The shell is allied to that of the marine genus 

 Skenea, and the body whirl is not modified by 

 the penultimate one. In the latter character it 

 approaches to some of the species of Amnicola, 

 and in the absence of the opercle, they cannot 

 be properly distinguished. 



The species are small in size and few in 

 number. Six recent and two fossil species are 

 described in Deshayes' Lamarck, all of which, 

 except V. tricarinata, occur in Europe. The 



