OBTMANN: monograph of the naiades of PENNSYLVANIA. 265 



locality is Chautauqua Lake (Marshall), and this undoubtedly has been reached 

 from the upper Allegheny. In Indiana (Call, 1896a, 1900) it is in the Ohio and 

 Wabash basins, and in some of the lakes in the northern part of this drainage, 

 Tippecanoe (Wilson & Clark, 1912a) Winona and Pike (Norris, 1902; Headlee, 

 1906), and here enters the Lake Michigan-drainage, St. Joseph basin (Call, 1900). 

 From Illinois it has been reported from the Wabash River (Baker, 1906). 



It is in the upper Monongahela and Elk River in West Virginia. Records from 

 Kentucky are lacking and Wilson & Clark (1914) do not report it from the Cumber- 

 land, but it is known from the Tennessee-drainage in Tennessee, Duck River, 

 Columbia, Maury Co. (Marshall, 1895), and is rather abundant in the headwaters 

 in East Tennessee, going up here to Virginia. 



It is unknown to the south and the west of this range. 



Little is known as to its ecology. Headlee (1906) gives some particulars with 

 regard to its occurrence in lakes. 



^ EuRYNiA (Micromya) IRIS (Lea) (1830). 



Lampsilis iris (Lea) Simpson, 1914, p. 113. 



Plate XVI, figs. 6, 7. 

 Records from Pennsylvania: 



Harn, 1891 (western Pennsylvania). 



Simpson, 1900, p. 553 (Beaver River, Pennsylvania) (as L. fatuus)."- 



Ortmann, 19096, p. 191. 



Characters of the shell: SheU of medium size, moderately thick anteriorly, 

 rather thin posteriorly. Outline subelliptical or subovate, moderately elongated, 

 about twice as long as high. Anterior and posterior ends rounded. Upper and 

 lower margins gently convex, the lower sometimes nearly straight. Beaks not 

 much elevated. Beak-sculpture consisting of four to six fine, but distinct, bars, 

 the first subconcentric, the others distinctly double-looped. Sometimes the later 

 bars become irregular. Valves convex, flattened upon the sides. No distinct 

 posterior ridge. 



Epidermis yellowish to light green, with dark green rays. The rays are more 

 or less distinct, sharply or poorly defined, rather narrow, straight, and mostly 

 not interrupted. Often there are concentric bands of color, indicating, in part, 

 the growth-rests. 



Hinge well-developed. Pseudocardinals two in left, one in right valve, tri- 

 angular, a little compressed and crenulated, not heavy. Interdentum absent. 



"' A specimen so labeled by Simpson is in the Carnegie Museum. 



