ORTMANN: monograph of the naiades of PENNSYLVANIA. 261 



South of the Ohio in Kentucky and Tennessee definite records are scarce. 

 Wilson & Clark (1914) give it from Stones River in Tennessee, a tributary of the 

 Cumberland. Call reports it (1885) from the Tennessee-drainage near Tuscumbia, 

 Alabama, and from Jackson, Hinds Co., Mississippi. But in this region and also 

 in Alabama it is supposed to be replaced by several other species, the standing of 

 which is very doubtful. 



According to Baker (1898a) and Scammon (1906), this is a species living 

 buried in mud, in sluggish streams, canals, etc. This is supported by my observa- 

 tions in Pennsylvania. 



Genus Eurynia Rafinesque (1820). 

 Ortmann, 1912, p. 336.'^' 



Type Unio recta Lamarck. 



Four species, and one variety are found in Pennsylvania. They fall into two 

 subgenera. 



Key to the Subgenera of Eurynia. 



«!. Inner edge of mantle in front of the brancliial opening in the female with irregular, larger or smaller 

 papillae, generally rather distant from each other. Shell small or of medium size, subovate or 

 subelliptical, not very long (hardly over twice as long as high). Glochidia subspatulate, con- 

 siderably higher than long Subgenus Micromya. 



0.2- Inner edge of mantle in front of brancliial opening in the female with a long row of quite regular, 

 uniform, smaller or larger papillfe, wliich stand rather crowded. Shell of medium or large size, 

 subelliptical, elongated, distinctly over twice as long as liigh. Glocliidia subovate, only slightly 

 liigher than long Subgenus Eurynia. 



Subgenus Micromya Agassiz (1852). 

 Ortmann, 1912, p. 337."° 



Type Unio fabalis Lea. 

 Two species and a variety in Pennsylvania. 



Key to the Forms of Micromya. 

 ffli. Shell very small. Hinge-teeth comparatively tliick and heavy. Rays faint, broad or fine, often 



somewhat undulating E. (M.) fabalis. 



ai. Shell larger, up to middle size. Hinge-teeth thin and delicate. Rays more or less distinct, not 

 undulating, but often interrupted. 



hi. Rays straight and continuous, often indistinct E. (M.) iris. 



hi. Rays interrupted, forming blotches, generally well-developed E. (M.) iris novi-eboraci. 



^^^ Eurynia (as subgenus of Lampsilis) Simpson, 1914, p.' 60, is only in part identical with Eurynia 

 in our sense. 



i'" The genus Micromya of Simpson (1914, p. 32) contains two species, of which only the first 

 (fabalis) belongs here. The other species of Micromya in our sense stand under Lampsilis Simpson. 



