79 



arcuate, carinated; posterior margin dilated, direct, 

 produced, and rounded or subtruncated at base; disks 

 covered with small subequal tubercles, arranged more 

 or less in symmetrical lines; within white. 



SYNONYMES. 



V. apiculatus, Say. Disseminator, 1829. American Conch. 



pi. 52. 

 U. asper, Lea. Trans. Amer. Phil. Soc, new series, vol. iii. p. 



95, pi. ix. fig. 15, 1832. 

 Cab. A. N. S. No. 1877. 



OBSERVATIONS. 



Inhabits the Alabama river, near Claiborne, where 

 I found specimens, but they were not numerous nor 

 comparable in beauty to those which inhabit Bayou 

 Teche in Louisiana. 



Mr. Say thinks this may prove to be a variety of 

 U. quadrulus, but although it is nearly related to that 

 species we believe it to be very distinct. Old shells 

 become proportionally more elongated and produced 

 at the posterior extremity of the basal margin, and 

 the tubercles nearly disappear on the inferior half of 

 the disks. The figure is from a specimen from Bayou 

 Teche. 



UNIO PRASINUS. 



Plate XLIV.— Fig. 2. 



DESCRIPTION. 



Shell suborbicular, compressed, with distant con- 

 centric impressed lines; anterior margin obtusely 



