OP CONCHOLOQY. 307 



3. Arionta, Leach. Globosely turbinate ; lip thickened 



within, expanded, dilated at the base so as nearly to 

 cover the umbilicus. Color yellowish-brown, banded. 

 Size large. 



Inhabits California and Oregon. 



4. Polymita, Beck. Globosely turbinate; lip much thick- 



ened within ; columella diagonal, much thickened, and 

 frequently bearing a lamelliform or rounded tubercle; 

 umbilicus almost entirely covered. Shell large, thick, 

 flesh-color, with generally several revolving bands of 

 darker colors. 



Inhabits West Indies. Mexico, Southern California. 



** Shell imperforate. 



5. Tachea, Leach. Shell imperforate, turbinate or de- 



pressed, upper whorls flattened, last one convex, de- 

 scending obliquely to the mouth, which is obliquely 

 semicircular ; peristome expanded, within labiate, ex- 

 panded and appressed into and completely covering the 

 umbilicus. Size moderate. Yellowish, more or less 

 numerously banded. 



European, introduced into the seaports and islands of the 

 Eastern States. 



6. Pomatia, Beck. Globular, large, last whorl very large, 



ventricose, deflexed at the aperture, which is orbicular 

 \y lunate ; peristome slightly thickened within, reflexed 

 and appressed over the umbilicus. Light horn-color, 

 banded. 



European, introduced into the seaports of the Southern 

 States and West Indies. 



HYGKOMIA, Eisso. 



The five species here united, evidently constitute two dis- 

 tinct groups; the two first species being of European origin, 

 while the other three belong to the Territories bordering on 

 the Gulf of Mexico : yet we can find no characters of sufficient 

 importance to justify their division into two generic groups. 



