102 NEW UNIONISE OF THE 



posterior slope is well marked in the lines of growth in all the specimens, old and 

 young. 



Unio Sampsonii. PI. 25, fig. 261. 



Tcstii lasvi, obliqua, inflatft, ad umbones valde tumida, postioc emarginata, antice rotunda, valde 

 inaequilaterali; valvulis crassis, antice paulisper crassioribus ; natibus prominentibus, tumidis, inour- 

 vis, ad apices vix undulatis; epidermide luteola, radiis viridis vestitis; dentibus cardinalibus 

 subgrandibus, erectis corrugatisque ; lateralibus crassis, curtis, corrugatis subrectisque ; niargarita, 

 argentea et paulisper iridescente. 



Shell smooth, oblique, inflated, very much swollen at the umbones, emarginate 

 behind, round before, very inequilateral ; valves thick, slightly thicker before ; 

 beaks prominent, swollen, incurved, slightly undulate at the tips ; epidermis yellow- 

 ish, covered with green rays ; cardinal teeth rather large, erect and corrugate ; 

 lateral teeth thick, short, corrugate and nearly straight ; nacre silver white and 



slightly iridescent. 



Proc. Acad. Nat. Sci., 1861, p. 392. 

 Hob. — Wabash River, New Harmony, Indiana, Mr. James Sampson. 

 My cabinet and cabinets of Mr. Sampson and Mr. Postell. 

 Diam. 1, Length l - 2, Breadth 1*7 inch. 



Shell smooth, oblique, intlated, very much swollen towards the umbones, emargi- 

 nate behind and round before, very inequilateral, with a low ridge on the middle 

 towards the margin, in front of which the disk is impressed, forming an obtuse 

 angle on the inferior posterior margin ; substance of the shell thick, slightly thicker 

 before ; beaks prominent, swollen, incurved and slightly undulate at the tips ; liga- 

 ment small and light brown ■ epidermis yellowish and covered with green rays over 

 the whole disk, with two distant marks of growth; umbonial slope but slightly 

 raised and rounded ; posterior slope narrow, with two obscure, impressed lines on 

 each valve, from the beaks to the posterior margin ; cardinal teeth rather large, 

 erect, corrugate and disposed to be trifid in the right valve ; lateral teeth thick, 

 short, corrugate and nearly straight; anterior cicatrices distinct, rather small and 

 deeply impressed ; posterior cicatrices distinct, rather large and well impressed ; dor- 

 sal cicatrices placed above the centre of the cavity of .the beaks ; cavity of the shell 

 rather deep and rounded ; cavity of the beaks somewhat deep and subangular ; nacre 

 silver white and slightly iridescent. 



Remarks. — Some two years since Mr. Postell, of Georgia, sent me several' speci- 

 mens, to me evidently young, of a species he did not know, having procured them 

 from Mr. Sampson, of New Harmony. Recently I sent a valve of one of these 

 specimens to Mr. Sampson, with an inquiry if he had found others like them and 

 larger or full grown. That gentleman very kindly promptly sent me a fine suite, 

 males and females of different ages, stating that it had been considered to be the 



