77 



Ravenel. I found it in the upper part of the Black 

 Warrior river, Alabama, where it is rare. 



Resembles U. perovatus in outline, but the shell is 

 far greater in diameter through the umbones, and the 

 beaks nearer the anterior extremity. The most 

 striking character, perhaps, is the accurate wedge- 

 shaped form of the posterior side. Mr. Lea first 

 published this species under the name of Ravcnclianus, 

 but as I had previously published a different species 

 with the same name, I am compelled to substitute 

 another. 



UNIO OBLIQUUS. 



Plate XLIIL— Fig. 2. 

 DESCRIPTION. 



Shell ovate-rotundate, oblique; disks with a slight 

 narrow furrow on the posterior side; umbonial slope 

 carinated; posterior slope with an obtuse carinated 

 line; ligament and posterior margins arcuate; posterior 

 extremity obliquely truncated; beaks very prominent, 

 curving forward; lunule sagittate; within white; car- 

 dinal teeth directed obliquely backwards; lateral teeth 

 arcuate; cardinal plate much thickened under the 

 cardinal teeth, contracting the cavity of the umbo. 



SYNONYMES. 



U. obliqua, Lam. An. sans Vert., vol. vi. p. 72. Fcrus. Mag. 



de Zool. 

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



p. 94, pi. ix. fig. 14. 

 Cab. A. N. S. No. 1259. 



