46 LAND AND FRESII-WATER SHELLS OF N. A. [PART III. 



Halderaan, I find roug'li figures (fig. 92) of 21. decisa under the 

 name of Ambloxis, Aniblodoma, or Lymnulus major, Ilafinesque, 

 or Lymnea eburnea, Rafinesque. AH these names are given, 

 and I find it impossible to decide which was the one finally fixed 

 upon, or to decipher more of the description than the follow- 

 ing :— 



Whirls 5, last very large, form obtuse oval, aperture obtuse oval, lip 

 thickened witliin, columella covered with callus. (Rajinesque.) 



I put Melania ovularis, Mke., in the synonymy on the authority 

 of Kiister (Chemn. ed. nov.), who so quotes it. I have seen no 

 authentic specimen, but cannot doubt its identity with 31. decisa. 



Melania ovularis, Menke, (1. c.) — Shell ovate-couoid, 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. 



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



Paludina limosa, Talenciennes, is considered a synonym of 

 M. decisa by Haldeman and Kiister. I have seen no authentic 

 specimen. It is also considered a synonym by Reeve, I. c. 



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

 phanous, green; whirls 5, longitudinally striate; labrnm 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. 



Tlie 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 Bulimus decollatus. 



I saw one individual Whose three ajjical whirls were destroyed so as to 

 give a broken appearance to the shell. 



Length rather more than one inch. ( Vcdenciennes.) 



The following also is cited as a synonym of M. decisa by Reeve. 

 Judging from the description I should so consider it. 



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

 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- 



