89 



OBSERVATIONS. 



Inhabits Cumberland river near Nashville, Ten- 

 nessee, and Elk river, near the muscle shoals, Ala- 

 bama. 



In outline it somewhat resembles Unio lineolatus, 

 but more nearly approaches the penitus. The rays, 

 very wide umbo, and the proportionally shorter out- 

 line distinguish it from the latter species. The lower 

 figure represents the female. 



UNIO PLEXUS. 



Plate XLIX.— Figs. 1, 2. 



DESCRIPTION. 



Shell suboval, ventricose; posterior margin trun- 

 cated or obtusely rounded; posterior slope with nar- 

 row ribs; umbo flattened, with longitudinal undula- 

 tions; umbonial slope subangulated; beaks eroded, 

 not prominent; epidermis nearly black, wrinkled; 

 within purple; cardinal teeth direct; anterior muscular 

 impression very rough. 



Cab. Ji. N. S., No. 20421. 



OBSERVATIONS. 



This species was sent from Vera Cruz by the 

 American consul, Dr. Marmaduke Burrough. I am 

 unacquainted with its habitat. The larger speci- 

 men, of which an outline is given on the plate, much 

 resembles U. niger, but the undulations on the urn- 

 bones, the proportional length in the smaller speci- 



M 



