CHIEFLY OF THE UNITED STATES. 11 



obtusel}' biangular behind and round before ; substance of the shell thin, thicker be- 

 fore at the margin; beaks slightly prominent, undulate at the tips; ligament small, 

 thin and pale brown ; epidermis greenish, obscurely radiate, highly polished, with a 

 distant mark of growth ; umbonial slope slightly raised and rounded ; posterior slope 

 very narrow, slightly carinate, with two impressed lines in each valve from the beak 

 to the posterior margin ; cardinal teeth very small, tuberculate, slightly compressed ; 

 lateral teeth long, acicular and nearly straight ; anterior cicatrices distinct, rather 

 large, and moderately well impressed ; posterior cicatrices confluent, rather large and 

 slightly impressed ; dorsal cicatrices very small and placed behind the centre of the 

 beaks ; cavity of the shell shallow and wide ; cavity of the beaks very small, scarcely 

 perceptible : nacre bluish white and iridescent. 



Remarks. — Only a single specimen of this pretty little species was received. It may 

 not be full grown, but I doubt if it becomes much larger. It has some resemblance to 

 a young lanceolatus, (nobis), but differs in outline, not being so oblique, and is not of 

 the same color in the epidermis, this being more green. There is in this specimen 

 only one mark of growth, and that is about the middle of the disk and it is broad. 

 The beaks are not perfect, but they show two or three imperfect rather distant undu- 

 lations at the tips. 



Unio Weldonensis. pi. 3, fig. 8. 



Testa laevi, elliptica, subinflata, sublenticular!, in»quilaterali, postice subbiangulari, antice rotunda ; val- 

 Tulis subcrassis, antice parum crassioribus ; natibus subprominentibus ; epidermide tenebroso-fusea 

 vel viridi-fusca, radiata; dentibus cardinalibus parviusculis, crenulatis, in utroque valvule duplicibus ; 

 lateralibus prselongis, lamellatis subcurvisque ; margarita alba vel purpurea et iridescente. 



Shell smooth, elliptical, somewhat inflated, sublenticular, inequilateral, biangular 

 behind, round before ; valves rather thick, slightly thicker before ; beaks somewhat 

 prominent ; epidermis dark brown or greenish brown and rayed ; cardinal teeth 

 somewhat small, crenulate and double in both valves; lateral teeth very long, 

 lamellar and somewhat curved ; nacre white or purple and iridescent. 

 Proo. Acad. Nat. Sci., 186.3, p. 191. 



Hah. — Roanoke River, at Weldon, North Carolina, E. Emmons, M. D. 



My cabinet and cabinet of Dr. Emmons. 

 Diam. 1-4, Length 2-2, Breadth 4 inches. 



Shell smooth, elliptical, somewhat inflated, sublenticular, inequilateral, subbiangu- 

 lar behind and round befoi'e ; substance of the shell somewhat thick, slightly thicker 

 before ; beaks somewhat prominent ; ligament long, thick and dark brown ; epider- 

 mis dark brown in the old, inclining to greenish and being much rayed in the 

 younger, with distant marks of growth ; umbonial slope raised and rounded ; posterior 

 slope rather compressed and slightly carinate ; cardinal teeth rather small, crenulate 



