ORTMANN: monograph of the naiades of PENNSYLVANIA. 95 



not at all true for Pennsylvania. In the Ohio this shell is also found in great 

 numbers on the shell-banks, consisting of masses of dead and broken shells, the 

 interspaces filled with sand and gravel, in strong, steady currents. The same is 

 the case farther down the Ohio, where it is taken in immense numbers by the 

 clam-diggers, but rejected on account of the color of its nacre. 



General distribution: Type locality, Ohio River (Rafinesque). 



A common shell all along the Ohio from western Pennsylvania through Ohio, 

 West Virginia, Kentucky, Indiana, and lUinois. Also in the Mississippi in Illinois, 

 Iowa, and North to Minnesota, Winona Co. (See Holzinger, 1888). It goes onh^ 

 into the larger tributaries. In Ohio, it is in the Muskingum River at Marietta, 

 Washington Co. (Hildreth, 1828), but not in the Tuscarawas River; it occurs in 

 the Scioto River (Sterki, 1907a). In Indiana it is known from the Wabash (Call, 

 1900, Goodrich, 1914), and White River (Carnegie Museum). In Illinois it is 

 found in the V/abash, and also in the Kaskaskia and Spoon Rivers (Baker, 1906). 

 In Iowa, it is in the Wapsipinicon, at Independence, Buchanan Co. (Geiser, 1910). 

 In West Virginia, I have discovered it in Elk River (tributary to the Kanawha). 

 This river, and the Levisa Fork of the Big Sandy, are the smallest streams, in 

 which I have found it. 



Additional records from Kentucky are missing, but this species is known from 

 the Ciunberland, Tennessee, Duck, Holston, and Clinch Rivers in Tennessee. 



In addition, it is widely distributed in the Alabama-drainage. The connection 

 of this range with the main range seems to be over the Gulf plain; but this requires 

 fm'ther study. The form from Alabama is indistinguishable from the Ohio 

 form, but, judging from the material at hand, not quite so large. Eastward in 

 the Chattahoochee in Georgia this form passes into a still smaller form, called E. 

 incrassatus. 



Elliptic DiLATATUS (Rafinesque) (1820). 

 Unio gibbosus Barnes. Simpson, 1914, p. 597; Unio dilatata Rafinesque, 

 Vanatta, 1915, p. 555; Elliptio dilatata (Rafinesque) Utteeback, 1916, 

 p. 90. 



Plate VIII, fig. 2. 

 Records from Pennsylvania: 



Harn, 1891 (western Pennsylvania). 



Stupakoff, 1894 (Allegheny Co.). 



Marshall, 1895 (Allegheny River, Warren Co.). 



Rhoads, 1899 (Ohio River, Coraopolis, Allegheny Co., and Beaver, Beaver Co.j Beaver River, Wampum, 



Lawrence Co.). 

 Ortmann, 19096, p. 197. 



