16 NEW UNIONID^, MELANIDyE, ETC., 



Shell smooth, very wide, very much compressed, flattened at the sides, very 

 inequilateral ; valves thin, somewhat thicker before ; beaks a little prominent, 

 undulate at the tips ; epidermis brownish green, obscurely rayed ; cardinal teeth 

 very small, tuberculate, double in both valves ; lateral teeth very long, acicular 

 and straight ; nacre bluish white and iridescent. 

 Proo. Acad. Nat. Sci., 186a, p. 193. 



Hah. — Black Eock Landing, Cape Fear Eiver, North Carolina, E. Emmons, M. D. 



My cabinet and cabinet of Dr. Emmons. 

 Diam. -4, Length -8, Breadth 2*5 inches. 



Shell smooth, very wide, much compressed, flattened at the sides, very inequi- 

 lateral ; substance of the shell translucent behind, slightly thickened before ; beaks 

 slightly prominent, undulated at the tips ; ligament thin, very long and brown ; 

 epidermis brownish green, obscurely rayed, with strong distant marks of growth ; 

 umbonial slope raised towards the middle and angular; posterior slope com- 

 pressed, raised into a carina, with two impressed lines from the beaks to posterior 

 margin in each valve; cardinal teeth very small, tuberculate and double in both 

 valves ; lateral teeth very long, acicular and straight ; anterior cicatrices distinct, 

 rather small and slightly impressed ; posterior cicatrices confluent and very slightly 

 impressed ; dorsal cicatrices placed nearly in the centre of the cavity of the beaks ; 

 cavity of the shell very shallow and very wide ; cavity of the beaks scarcely per- 

 ceptible ; nacre bluish white and very iridescent. 



EemarJcs. — This species need not be confounded with any other with which I am 

 acquainted. It is nearest to naviculoides, (nobis), but it is a smaller shell and 

 wider in proportion. It difiers also in color, being greenish, and the posterior 

 biangular margin is not so broad. The cardinal teeth are also smaller, and the 

 form of the umbonial slope is very different. In perlatus the greatest transverse 

 diameter is nearly two- thirds down the umbonial slope. This is very characteristic 

 of this species. The superior cicatrix of the anterior group is placed over that of 

 the tractor muscle, and alongside and separate from the great adductor cicatrix. The 

 undulations of the beaks are not perfect, even in the youngest specimen before me, 

 but they are enough so to make out three or four, which are irregular and trans- 

 verse. The specimens before me have two or three marks of growth, the second 

 one being always broad and well defined. The posterior slope has the epidermis 

 iinbricate. 



Unio Waccamawensis. PL 5, fig. 14. 



Testa Iffivi, triangulari, inflata, ad latere planulata, valde inaequilaterali, postice subbiangulata, antice 

 rotundata; valvulis tenuibus ; natibug prominentibus; epidermide fusco-virente vel olivacea, 

 obsolete radiata; dentibus cardinalibus parvissiniis, compressis, obliquis, in utroque valvulo duplici- 

 bus ; lateralibus longis, lamellatis rectisque ; margavita cajruleo-alba et iridescente. 



