Dr. Hildreth on fresh water Shells. 279 



Length, 3,5 ; breadth, 5.00; diameter, 2.125. 



Shell long before, short behind, equally rounded at both 

 extremities ; beaks slightly projecting ; ligament elevated 

 above the beaks ; epidermis dark brown, lighter in young 

 specimens, and obscurely rayed — waved on the center of 

 the disks, and wrinkled transversely ; teeth deeply divided, 

 elevated and striated ; anterior cicatrix wrinkled, posterior 

 cicatrix rough behind and smooth before ; cavity of the 

 beaks moderate and angulated ; naker pearly and beauti- 

 fully iridescent on the forepart. 



Remarks. — I have a great many specimens of this shell, 

 from very young to old ; they are remarkably uniform in 

 their proportions. Its good qualities for eating, are said to 

 be equal to those of any other shell in these streams. 



No. 3. Unio Cuneatus. — Fig. 3. 



Shell ovate, wedge shaped, thick, gibbous ; disks swelled ; 

 a side view of the shell bearing a strong likeness to the head 

 of the bald eagle ; lateral teeth thick ; inside a rich rose 

 color. — Hab. Muskingum. 



Length, 3.00 ; breadth, 4.4 ; diameter, 2.00. 



Shell elongated and subtiiangular, thick and ponderous ; 

 anterior side narrowed, thin, angulated, wedge shaped, com- 

 pressed ; umboes large and elevated, beaks low and dis- 

 tant, much decorticated; anterior lunule, long heart shaped, 

 with an elevated ridge running from the beaks to the ante- 

 rior basal margin, and projecting on that part — basal mar- 

 gin slightly rounded and arcuated before ; anterior margin 

 narrow and angulated ; posterior margin rounded and broad ; 

 epidermis blackish brown ; surface wrinkled transversely. 

 Cardinal teeth deeply divided and sulcated ; lateral teeth 

 long, thick and striated ; cicatrices deep ; cavity of the 

 beaks small and rounded ; naker a rich rose color and irid- 

 escent. 



No. 4. Unio Undulatus. — Fig. 4. 



Shell rhombic ovate, with numerous waving folds radia- 

 ting from the beaks. 



Length, 4.00; breadth, 5.25; diameter, 2.00. — Hab. Duck 

 Creek. 



Shell thick, obtusely rounded, behind, emarginate before ; 

 beaks slightly elevated ; hinge margin sub-alated, compres- 

 sed, carinated with a furrow on each side ; anterior dorsal 

 margin sub-truncate ; epidermis blackish brown and finely 



