XX 



By some strange mistake, this genus is referred 

 by Messrs. II. & A. Adams to Vivipara. 



Rafinesque published several species; one of 

 which, p. verrucosa, is identical with Lithasia nu- 

 pera, Say, and therefore belongs to an entirely 

 different group. Others, however, are evidently 

 closely related to 31. canallculata, Say, and 31. ele- 

 vata, Say. The genus is certainly well characterized, 

 and clearly includes those shells which Mr. Swainson 

 has subsequently distinguished as Cerij^hasla, and 

 Mr. Lea as Trypanostoma. 



In the same Journal (p. 26), Rafinesque described 

 a genus ''Xe/^^ox-i^" as follows: ^'' Leptoxis. Differs 

 from Lymnula by an oval shell, inflated, the spire of 

 two or three whorls; aperture oval, almost as large 

 as the whole shell. Eyes exterior. About four 

 species, fluviatile, lacustrine and palustrine." 



There can be no doubt that this description was 

 intended for Ancidosa, Say, as is proved by a manu- 

 script work by Rafinesque (" Conchologia Ohioensis " ) 

 in the possession of the Smithsonian Institution, in 

 which there is a rude pen-and-ink drawing of the 

 animal and shell of a Leptoxis. The name has been 

 adopted by Prof Haldeman and others. But as the 

 published description refers equally well to species 

 of AmnicoUdce or Viviparidce, and as manuscript 

 authority is not recognized in questions of priority, 

 we are compelled to throw aside this name and 

 adopt that given by Say. 



In the manuscript quoted above, occurs the de- 

 scription of a new genus called Strepoma, together 

 with the figure of a species ; which appears to 

 represent a section of Pleurocera. It is unnecessary 

 to quote the description, as it was never published : 



Pleurocera, 1819, is perhaps a S. G. of Melania, but the animal is dif- 

 ferent, with lateral feelers; tlie shell is always conical oblong, with 

 the opening ol^long oblique acute at both ends, columella flexuose 

 twisted;" and, further, "I leave the name of Melania to the sliells 

 ■with the opening obtuse at the end; or they may form the S. G. Am- 

 bloxis." 



