4 VALVATA TRICARINATA. 



DESCRIPTION. 



ANIMAL slightly translucent, branchial fila- 

 ment long; eyes black and conspicuous; pos- 

 terior extremity of the foot extending nearly to 

 the circumference of the shell, and terminating 

 obtusely; opercle very near the extremity of 

 the upper surface of the foot, and visible 

 through the substance of it from the lower side. 



SHELL turbinate, translucent, having rather 

 more than 3 volutions, which are smooth and 

 prismoidal, with the lines of growth faint: spire 

 flattened: volutions much flattened between the 

 carinse; body whirl tricarinate; the posterior 

 carina revolving to the apex, and the medial 

 one just covered by the advance of the inner 

 margin of the aperture: base widely and deeply 

 umbilicate, umbilic bounded by the inferior 

 carina. Opercle thin, concave externally. 



COLOR greenish, or light chesnut-brown; 

 carinse whitish, with pale corresponding lines 

 within the shell. 



GEOGRAPHICAL DISTRIBUTION. Inhabits New 

 England and the Middle States. Say found it 

 common as far west as Council BlufF, and Dr. 



