10 



UNIO METANEVRUS. 



Plate V. Fig. 2. 



DESCRIPTION. 



Shell suboval, thick, ventricose; anterior side tu- 

 berculated, except near the margin, which is smooth; 

 disk with an oblique furrow; umbonial slope very 

 prominent, broad and rounded, with numerous tu- 

 bercles, some of which are very large; posterior slope 

 wide, concave, or angular, with oblique slightly re- 

 curved series of rib-like tubercles; umbo slightly 

 prominent; beaks retuse; ligament margin oblique, 

 rounded at the extremity; posterior margin emargi- 

 nate; epidermis yellowish-brown, with interrupted 

 green rays; within white, much thickened anteriorly. 



SYNONYMES. 



U. metanevra, Raj '. Ann. gen. des Sc Phys. vol. v. p. 39. 



Ferussac, Mag. de Zool. 

 U. nodosus, Barnes. Silliman's Journal, vol. vi. p. 124, pi. vi. 



fig. 7. 

 Cab. A. N. S. No. 1754. 



OBSERVATIONS. 



A common species in the western and southern 

 rivers, easily recognised, when in perfection, by its 

 swelling umbonial slope: very old specimens much 

 resemble U. stapes, Lea, but are much larger. 



