48 NEW UNIONID.E OF THE 



allied to any species known to me, and would not be easily confounded with any other. 

 The obovate form, the great inflation on the umbonial slope, and the thin diaphanous 

 nacre distinguish it at once. The specimen has all the appearance of being fully 

 grown, and yet the capillary rays and the two lines of growth may be distinctly seen 

 from the inside. The bluish nacre is exceedingly thin, and not reaching to the margin 

 within a tenth of an inch, leaves quite a broad border of the outer layer, which, under 

 the microscope, exhibts the subhexagonal cell structure, as may be seen also in thin 

 3'oung specimens of Unio gracilis (Barnes) and some other species.* The tooth of 

 each valve is small, and that in the right valve is more compressed, and locks in 

 anterior to that of the left valve. Mr. Anthony's specimen is j-ounger and smaller, 

 and has rays over the whole disk. 



Anodoxta Dariexsis. pi. 28, fig. 99. 



Testa Itevi, elliptica, ventricosa, injequilaterali, postici: obtus^ angulata; valvulis subteauibus, anticfe 

 paulisper crassioribus ; natibiis clevatis, tumidis, ad apices minute undulatis ; epidermide tenebroso- 

 oliva, striata, obsolete radiata; margarita caeruleo-alba et irideseente. 



Shell smooth, elliptical, ventricose, inequilateral, obtusely angular behind; valves 

 rather thin, slightly thicker before ; beaks raised, swollen, minutely undulate at the 

 tips ; epidermis dark olive, striate and obsoletely radiate ; nacre bluish white and 

 iridescent. 



Proc. Acad. Nat. Sei., 18.J8, p. 139. 



Jiah. — Hopeton, near Darien, Georgia, J. Hamilton Couper, Esq. Swift Creek, near 

 Macon, Georgia, Bishop Elliott and J. C. Plant; and Flint Piiver, Georgia, Dr. 

 Neisler. 



My cabmet and cabinets of Mr. Couper and Bishop Elliott. 

 Diam. 2, Length 2-.3, Breadth 4-2 inches. 



Shell smooth elliptical, ventricose, inequilateral, obtusely angular behind and 

 rounded before; substance of the .shell rather thin, slightly thicker before; beaks 

 raised, swollen, with several small, transverse undulations on each tip ; ligament rather 

 long, somewhat thick and brown ; epidermis dark olive, striate, obscurely rayed, with 

 distant marks of growth, and disposed to have dark and yellow transverse bands ; 

 umbonial slope very much inflated and rounded ; posterior slope very wide, somewhat 

 raised, with a raised line and three green rays passing from the beaks to the posterior 

 margin ; anterior cicatrices confluent, rather large and slightly impressed ; posterior 

 cicatrices large, confluent and very slightly impressed ; cavity of the shell very deep 

 and wide; cavity of the beaks rather shallow and rounded; nacre bluish white and 

 iridescent. 



tSo/i parts. — Branchial uterus . Among ten specimens received only one had 



* It may be remembered that the substance of the valve of the Uiilonidce, is made up of three parts, viz., 

 the nacre, the cell structure and the periostracum. 



