48 DESCRIPTION OF FIFTY-TWO SPECIES OF TJNIONIDiE. 



of the shell somewhat thick ; beaks small, a little prominent and rugosely undulate 

 at the tips ; ligament rather long, narrow and dark brown ; epidermis dark brown, 

 somewhat squamose, without rays, with distant and well-marked lines of growth ; 

 umbonial slope very slightly raised and obtusely angular ; posterior slope slightly 

 carinate and very narrow elliptical ; cardinal teeth small, sulcate, compressed coni- 

 cal and double in both valves; lateral teeth very long, lamellar and nearly straight; 

 anterior cicatrices distinct, very large and well impressed ; posterior cicatrices con- 

 fluent, large and slightly impressed; dorsal cicatrices placed nearly in the centre of 

 the cavity of the beaks; cavity of the shell shallow and wide; cavity of the beaks 

 scarcely observable; nacre white and very iridescent. 



Remarks. — Mr, Wheatley has furnished me with seven specimens of this species. 

 In outline it is nearest to rostrum (nobis). It is somewhat squamose like squameus 

 (nobis), but it differs in outline and the beaks are more medial. There is a strong 

 disposition to sulcation on the exterior, particularly on the anterior portion of the 

 valve. 



Unio basalis. pi. 16, fig. 46. 



Testa Iffivi, oblonga, subinflata, ad latere subplanulata, insequilaterali, postice obtuse biangulari, antice 

 rotundata, ad basira recta; valvulis crassiusculis; natibus prominulis; epidermide luteola, radiata; 

 dentibus cardinalibus parviusculis, subcompressis, sulcatis ; iJfteralibus sublongis, lamellatis cur- 

 visque ; margarita vel albida vel purpurascente et iridescente. 



Shell smooth, oblong, somewhat inflated, flattened at the sides, inequilateral, 

 obtusely biangular behind, rounded before, straight at the base ; valves somewhat 

 thick; beaks a Kttle prominent ; epidermis yellowish and radiate; cardinal teeth 

 rather small, rather compressed, sulcate ; lateral teeth rather long, lamellate and 

 curved ; nacre white or purple and iridescent. 

 Proc. Acad. Nat. Sci., 1812, p. 161. 



2ya&.— Carter's Creek, near Columbus, Georgia, G. Hallenbeck. 



My cabinet. 

 Diam. -8, Length 1-5, Breadth 2-5 inches. 



Shell smooth, oblong, somewhat inflated, flattened at the sides, inequilateral, 

 obtusely biangular behind, rounded before, straight at the base ; substance of the 

 shell somewhat thick ; beaks a little prominent ; ligament short, thick and dark 

 brown ; epidermis yellowish, rayed, with rather close marks of growth ; umbonial 

 slope raised and rounded ; posterior slope carinate, narrow elliptical ; cardinal teeth 

 rather small, somewhat compressed and sulcate ; lateral teeth rather long, lamellar 

 and curved; anterior cicatrices distinct, rather small and well impressed; posterior 

 cicatrices confluent, large and moderately well impressed ; dorsal cicatrices placed 



