NEW FRESH WATER AND LAND SHELLS. 213 



Unio Bofrnianus. Plate 15, Fig. 28. 



Testa triangulari, compressd; valvulis crassis; natibus elevatis, incurvis, ad apices undulatis ; epider- 

 mide luted, dense radiatd; dentibus cardinalibus subgrandibus ; later alibiis subcurvis; mar gar itd alba 

 et iridescente. 



Shell triangular, compressed; valves thick; beaks elevated, incurved and undulated at the tip; epidermis 

 yellow, much radiated ; cardinal teeth rather large ; lateral teeth somewhat curved ; nacre white and iri- 

 descent. 



Hab. Scioto River, near Chillicothe, Ohio. A. Bourne. 

 My Cabinet, and Cabinet of Mr. Bourne. 

 Diam. .7, Length 1.2, Breadth 1.2 inches. 



Shell triangular, very much compressed behind the umbonial slope, swollen 

 over the umbones; substance of the shell very thick, thinner towards the pos- 

 terior basal margin ; beaks elevated, very thick and solid, incurved and undu- 

 lated at the apex; ligament short and thin; epidermis yellow with numerous 

 interrupted rays nearly over the whole disk, the lines of growth being very dis- 

 tinct; cardinal teeth rather large and broad; lateral teeth thick and somewhat 

 curved ; anterior cicatrices distinct, the superior one very deep ; posterior cica- 

 trices distinct, and placed on the end of the lateral tooth ; dorsal cicatrices placed 

 rather under the cardinal tooth ; cavity of the shell shallow ; cavity of the beaks 

 shallow and angular ; nacre white and iridescent. 



Remarks. — This species seems only to have been observed by Mr. Bourne, 

 by whose kindness I have before me the two specimens found by him. In 

 outline, general form and solidity it resembles most TJ. pyr'amidatus, (nobis.) 

 It differs entirely in the epidermis being yellow and having rays, and in the 

 nacre which has no appearance of colour whatever in either specimen. In one 

 individual beautiful green rays cover the disk — in the other they do not reach 

 to the anterior margin. The epidermis in both is remarkably yellow. I name 

 it after the naturalist Mr. Bourne, who has first observed it. 



Unio paulus. Plate 15, Fig. 29. 



Testa ellipticd, injlatd, minima; valvulis crassis; natibus subprominentibus; epidermide subnigrd; 

 dentibus cardinalibus parvis ; later alibus longis curvisque; margaritd albd et iridescente. 



