CHIEFLY OF THE UNITED STATES. 319 



Soft parts. — Three young specimens, not half grown, were received. None had 

 ova in the ovarium or embryos in the branchial uterus. Branchice rather small and 

 rounded, the inner ones the larger, united the whole length of abdominal sack. Paljji 

 small, ovate, united at the upper posterior edges. Mantle very thin, thicker on the 

 edges. Branchial opening rather large, with small dark papillse. Anal opening very 

 small, with numerous, very small papillae on the inner edges. Super-anal opening 

 rather large and edged with black. Color of the mass whitish. 



Remarlcs. — This species belongs to the complanatus group. It is closely allied to 

 those of that portion of it which is disposed to be biangular behind. It differs in 

 being less carinate, having rather thicker teeth, and it differs also somewhat in the 

 rays. Of the two specimens before me, one has a deep purple nacre throughout, the 

 other is salmon color in the cavity, but towards the margin it is white. I have no 

 doiibt that specimens will be found of a full salmon color and others entirely white. 

 These two specimens were sent to the Smithsonian Institution by Dr. Strebel, of Vera 

 Cruz, and to him I dedicate the species. 



Unio sph^ricus. pi. 51, fig. 132. 



Testa noduiosa, subrotunda, valde inflata, subglobosa, fere jequilaterali ; valvulis crassis, antice cras- 

 sioribus ; natibus elevatis ; epidermide rufo-castanea, eradiata ; deotibus cardinalibus pergrandi- 

 bus, corrugatis crenulatisque ; lateralibus curtis, crassis, corrugatis, obliquis subcurvisque ; mar- 

 garita argentea et valde iridescente. 



Shell nodulous, rotund, very much inflated, subglobose, nearly equilateral ; valves 

 thick, thicker before ; beaks raised ; epidermis reddish chestnut color, without rays ; 

 cardinal teeth very large, corrugate and crenulate ; lateral teeth short, thick, corru- 

 gate, oblique and somewhat curved; nacre silver white and very iridescent, 

 Proc. Acad. Nat. Sci. 1868, p. 145. 



nab. — Pearl River, at Jackson, Mississippi, C. M. Wheatley. 



My cabinet and cabinet of Mr. Wheatley. 

 Diam. 1-3, Length 1-8, Breadth 1-9 inch. 



Shell nodulous, rounded, very much inflated, subglobose, nearly equilateral ; sub- 

 stance of the shell thick, thicker before ; beaks raised and recurved ; ligament short, 

 thick and dark brown ; epidermis reddish-chestnut color, with rather distant marks 

 of growth ; umbonial slope raised and obtusely angular ; posterior slope cordate and 

 slightly raised into a carina; cardinal teeth very large, corrugate and crenulate ; 

 lateral teeth short, thick, corrugate, oblique and somewhat curved ; anterior cicatrices 

 distinct, rather small and very deeply impressed ; posterior cicatrices confluent, large 

 and well impressed ; dorsal cicatrices placed on the base of the cardinal teeth ; cavity 

 of the shell deep and rounded; cavity of the beaks deep and obtusely angular; nacre 

 silver white and iridescent. 



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