208 ' DESCRIPTION OF 



Unio Boykinianus. Plate 13, Fisr. 22. 



Testa alatu,plicata, triangulari, subcompressd ; valvulis crassis; natibus prominulis ; epidermide tene- 

 broso-fuscd ; dentibus cardinalibus parvis ; lateralibus sublongis ; margarita alba et iridescente. 



Shell winged, folded, triangular, rather compressed; valves thick; beaks somewhat prominent; epidermis 

 dark brown; cardinal teeth small; lateral teeth rather long; nacre white and iridescent. 



Hab. Chattahoochee River, Columbus, Geo. Dr. Boykin. 



My Cabmet. 

 Diam. .1.2, Length 2.2, Breadth 2.8 inches. 



Shell winged, folded all over the disk, triangular; rather compressed; sub- 

 stance of the shell thick; beaks somewhat prominent; ligament short and thin; 

 epidermis dark brown ; cardinal teeth small, apparently divided into three lobes 

 in each valve ; lateral teeth rather long and slightly curved ; anterior cicatrices 

 distinct ; posterior cicatrices confluent ; dorsal cicatrices on the under side of 

 the plate near to the cardinal tooth; cavity of the shell rather deep; cavity of 

 the beak angular ; nacre white and iridescent. 



Remarks. — I owe to the kindness of Dr. Boykin this fine species, as well as 

 many others herein described from the same locality. It has perhaps more re- 

 semblance to U. NicMinianus (nobis,) than to any other species in its outline, 

 and its folds, which latter are, however, larger. On the posterior slope the folds 

 are very regular, on the other part, less so. I have had in my possession many 

 years a young individual from the late Judge Tait, much resembling this, 

 and it may prove to be the same species. The geographical distribution of 

 the species of this family is of great interest and very important in many re- 

 spects, as we find a marked distinction in nearly all the different species respec- 

 tively inhabiting the waters east and west of the mountains, as I have elsewhere 

 observed. For many years I have been exceedingly desirous of obtaining the 

 shells inhabiting the approximating waters which fall respectively into the 

 Atlantic on one side, and the Gulf of Mexico east of the Mississippi, on the 

 other. The Chattahoochee is the first river of magnitude rising in the moun- 

 tains which descends to the gulf, unless the Flint river be excepted. Amono- 

 the species from this locality now under examination, I find three with folds 

 (none with tubercles,) which, as we do not possess any in our eastern rivers, may 

 be considered to have the western character. The remainder in part resemble 



