87 



OBSERVATIONS. 



Inhabits the Alabama and Black Warrior rivers: 

 rare. 



This is one of the smallest species of Unio, and 

 resembles the young of the conradius, but is much 

 more elongated. Mr. Lea observes that the lateral 

 teeth are single in each valve; but the specimens be- 

 fore me have the usual form of a divided tooth in the 

 left valve. The epidermis is marked with pale green 

 zig-zag lines, and the furrows on the disk are some- 

 times obsolete or wanting. I found two fine indi- 

 viduals at the village of Erie, Greene county, Ala- 

 bama, on a bar in the Black Warrior river. 



UNIO CONRADIUS. 



Plate XLVIL— Fig. 3. 



DESCRIPTION. 



Shell elliptical, basal margin straight or slightly 

 emarginate; ligament margin slightly declining; valves 

 rather thin, with undulations on the posterior side, 

 sometimes obsolete; posterior slope with arcuate 

 ribs; beaks very slightly prominent and undulated, 

 decorticated; epidermis finely wrinkled, yellowish- 

 brown, with numerous green rays; within inclining 

 to salmon colour; very iridescent and furrowed pos- 

 teriorly. 



SYNONYME. 



U. conradius, Lea. Trans. Amer. Phil. Soc, new series, vol. v. 



p. 63, pi. ix. fig. 23. 

 Cab. A. N. S., No. 20419. 



