88 



OBSERVATIONS. 



Inhabits Flint river, Alabama, near its junction 

 with the Tennessee river, and is common in the 

 vicinity of Nashville, Tennessee. This small species 

 is related to U. subtentus, but is very obviously dis- 

 tinct. It is proportionally shorter than the acutissimus, 

 and has more obvious beaks, but young individuals 

 much resemble the latter species, as may be observed 

 in fig. 4. In some specimens the posterior undula- 

 tions are large and profound, in others more nume- 

 rous and not so distinct. 



UNIO INTERRUPTUS. 



Plate XLVIII. 



DESCRIPTION. 



Shell subtriangular, disks flattened; umbones broad, 

 flattened, summits obtusely rounded; posterior slope 

 much depressed; umbonial slope abruptly rounded, 

 nearly terminal; epidermis brownish-yellow, wrinkled, 

 except on the umbo; rays numerous, narrow, inter- 

 rupted, of a dark olive colour; on the umbonial and 

 posterior slopes consisting of series of small quad- 

 rangular spots; within white; cardinal and lateral 

 teeth very robust; anterior and posterior muscular 

 impressions deeply impressed. 



SYNONYMES. 



U. interrupta, Raf. Ann. gen. des Sc. Phys., vol. v. p. 36. 



Say. Amer. Conch., No. 6. Ferr. Mag. de Zool. 

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



iv. p. 75, pi. vi. fig. 6. 

 Cab. J. N. S., No. 1114. 



