ORTMANN: monograph of the naiades of PENNSYLVANIA. 289 



in West Virginia not only in the headwaters of the Monongahela, but also in the 

 Little Kanawha, in the Kanawha and Guyandotte drainages; but that it is absent 

 here in certain regions, for instance, in the Elk River of the Kanawha sj^stem. 

 This no doubt is due to the rough character of Elk River. In addition I found 

 this species in the Licking River in Kentucky. But it actually seems to be absent 

 in the Cumberland and Tennessee River drainages. 



In a westward and southwestward direction this species undoubtedly goes as 

 far as Missouri (Utterback, 1916), Kansas (Scammon, 1906), Arkansas, and Okla- 

 homa, and has been reported to exist in Texas (Brazos River, Simpson, 1900). 

 However, in this region it. passes into other forms {hydiana, for instance) which 

 may, or may not be, "good species." In Mississippi and Alabama it seems to be 

 represented by kindred forms, which are generally considered to be different 

 species. 



Thus L. luteola has its main range chiefly in the northern section of the Interior 

 Basin, north of the Ohio, and passes into the northern drainages of the St. Lawrence 

 and Hudson Bay. But in the north, as well as in the south, it inclines to variation, 

 and has developed geographical and local races, some of which may be regarded 

 as valid species. 



Both Baker (1898a) and Scammon (1906) call this a mud-loving species, which 

 agrees with my observations. Although sometimes found in other environment, 

 it thrives best and is most abundant in mud and sluggish or quiet water. This 

 satisfactorily explains its absence in certain streams in western Pennsylvania and 

 West Virgmia, and possibly also in the Tennessee-Cumberland-drainage. This 

 also holds good in the Ohio River between Pennsylvania and Cmcinnati. I found 

 it in the Ohio at Toronto, in a small branch of the river, but at no other locality, 

 and it was entirely missing in the numerous piles of the clam-diggers examined by 

 myself. 



Lampsilis luteola rosacea (DeKay) (1843). 

 Lampsilis luteola rosacea (DeKay) Simpson, 1914, p. 62; Walker, 1913, p. 21. 



Plate XVII, figs. 3, 4, 5. 



Record from Pennsylvania: 



Ortmann, 19196, p. 202 (as lake-form of L. luteola). 



Characters of variety: This may be described as a small, stunted form of L. 

 luteola, generally with rather light-colored (pale yellow to rusty) epidermis, with 

 white or (locally) rosaceous nacre. The specimens from Lake Erie (and also other 

 lakes) have generally more regular, more crowded, and more distinct growth-rests. 



