86 



has some resemblance to U. purpureus, Nob.; but it 

 is distinguished by many characters, and more ob- 

 viously by the character of the anterior costated 

 margin. It is a native of South Carolina,* and was 

 sent to me by Professor Vanuxem, who obtained it 

 from the North Fork of the Holston river." 



Dr. William Blanding presented me with specimens 

 from Nollichucky river, Tennessee, the largest of 

 which is nearly destitute of the posterior ribs. I 

 found a few dead shells on the bank of Elk river, 

 near the muscle shoals, Alabama. 



UNIO ACUTISSIMUS. 



Plate XLVIL Fig. 2. 



DESCRIPTION. 



Shell narrow-elliptical; posterior side produced, 

 gradually narrowed to a point; valves thin; posterior 

 side with parallel furrows extending from the umbo- 

 nial slope to base; posterior slope with slightly arcuate 

 ribs and furrows; umbonial slope carinated; beaks 

 not elevated above the dorsal line; epidermis yellow- 

 ish, with green dotted rays; within yellowish, highly 

 polished, exhibiting the ribs of the exterior. 



SYNONYME. 



U. acutissimus, Lea. Trans. Amer. Phil. Soc. , new series, vol. 



iv. p. 89, pi. x. fig. 18. 

 Cab. A.N. S.,No. 20418. 



* Mr. Vanuxem informs me that he found it in Virginia. 



