ORTMANN: monograph of the naiades of PENNSYLVANIA. 285 



rays. Young specimens of Adinonaias ligamentina sometimes resemble this species, 

 but their shape is more broadly elliptical. Large individuals of Eurynia iris also 

 might be mistaken for L. luteola, but they have a more elongated shape, more 

 iridescent nacre, and besides the character of the rays is different. 



In old specimens the epidermis is often more or less discolored, and the smooth- 

 ness disappears, but specimens with dark (brown or black) epidermis are very 

 rare. The typical inflation of the valves is best developed in old individuals, 

 while young ones are generally more or less compressed. 



Several forms (or species) have been distinguished. The variety rosacea will 

 be discussed below. But there are other local forms, which, however, are not 

 constant enough to deserve special mention, and most of them are not found in 

 our state. 



Localities in Pennsylvania represented in the Carnegie Museum: 



Ohio River and Ohio-drainage: 

 Ohio Eiver, Cooks Ferry and Industry, Beaver Co.; Coraopolis (S. N. Rhoads) and Neville Island, 



Allegheny Co. 

 Buffalo Creek, Aeheson, Wasliington Co. 

 Little Beaver Creek, Cannelton (Miss Vera Wliite & H. H. Smith), Darlington, and New Galilee, Beaver 



Co.; Enon Valley, Lawrence Co. 

 Raccoon Creek, Raccoon Townsliip, and New Sheffield, Beaver Co.; Bavington, Washington Co. 

 Chartiers Creek, Carnegie, Allegheny Co. (D. A. Atkinson & J. L. Graf). 

 Little Chartiers Creek, Morganza, Washington Co. 



Beaver-drainage: 

 Beaver River, Wampum, Lawrence Co. (G. H. Clapp & H. H. Smith). 

 Connoquenessing Creek, Zelienople and Harmony, Butler Co. 

 Slipperyrock Creek, Wurtemberg and Rose Point, Lawrence Co. 

 Wolf Creek, Grove City, Mercer Co. 

 Brush Creek, Celia, Beaver Co. 



Little Connoquenessing Creek, Harmony, Butler Co. 

 Glade Run, Zeno, Butler Co 

 Thorn Creek, McBride, Butler Co. 

 Bonnie Brook, East Butler, Butler Co. 



Mahoning River, Mahoningtown, Coverts, Edinburg, and Hillsville, Lawrence Co. 

 Neshannock Creek, Volant, Lawrence Co.; Leesburg, Mercer Co. 

 Shenango River, Harbor Bridge and Pulaski, I awrence Co.; Sharpsville, Clarksville, Shenango, and 



Jamestown, Mercer Co.; Linesville, Crawford Co. 

 Pymatuning Creek, Pymatuning Townsliip, Mercer Co. 

 Little Shenango River, Greenville, Mercer Co. 

 Randolph Run, Hartstown, Crawford Co. 

 Padan Creek, Linesville, Crawford Co. (0. E. Jennings). 



