VIVIPARA. 



25 



indented ; aperture subovate, less than half of the 

 length of the shell. 



Inhabits the waters of the Missouri. Length ^ 

 inch. 



Very much resembles P. decisa; the spire, how- 

 ever, is more elongated, and never truncated at 

 the apex, but always acute. {Say.) 



I put Ilelania ovularis, Mke., in the syu- 

 onymy on the authority of Kiister (Chemn. 

 ed. nov.), who so quotes it. I have seen 

 no authentic specimen. 



Fig. 38. 



Paludina inUgra. 



Melania ovularis, Menke, (1. c.) — Shell ovate-conoid, truncate, substriate, 

 shining, greenish, reddish-brown when old, truncated at apex ; aperture 

 ovate, columella subcallous above ; aperture rounded before. 



Length 1 inch ; breadth 7 lines. 



Ilab. — Near Cincinnati, in the Ohio River. Bescke. (Menke.) 



Paludina limosa, Yalenciennes, is considered a synonym by 

 Halderaan and Kiister. I have seen no authentic specimen. 



Paludina limosa, Valenciennes (1. c.) — Shell ovate-conic, thin, subdia- 

 phanous, green ; whirls 5, longitudinally striate ; labrum acute. 

 Paludina limosa, Say, Journ. Phil. I, 125. 



This Paludina is less globose and longer than that of our climate. The 

 height at the last whirl is a little less than of the others. Its breadth is 

 greater than its length, and its surface is covered with somewhat strong 

 longitudinal striae. The form of the aperture is also more oval. Its ver- 

 tical diameter is the longest. 



The lip is sharp, continued to the columella, which is not appressed. 



The shell is not very thick ; there are, however, some individuals which 

 are eroded like some of the bivalve shells. 



The apex is destroyed as the animal grows, and a flat circular partition 

 is formed, having the axis of the shell in its centre, in about the same 

 manner as in Bxdimus decollatus. 



I saw one individual whose three apical whirls were destroyed so as to 

 give a broken appearance to the shell. 



Length rather more than one inch. {Valenciennes.) 



The following also is cited doubtfully as a synonym by Halde- 

 man. I have seen no specimen. 



Paludina cornea, Valenciennes (1. c.) — In the Delaware and many other 

 rivers of the United States there is found a horn-colored Paludina, which 

 at first sight resembles the Pal, limosa, but which a more careful examina- 



