ORTMANN: monograph of the naiades of PENNSYLVANIA. 11 



proper and some of its larger tributaries. Of the latter outside of Pennsylvania 

 the Tuscarawas and Scioto Rivers contain it (Sterki, 1907a); it is in the Illinois 

 River in Illinois (Baker, 1906). Call (189Ga) does not mention this species from 

 Indiana, but he unites it with F. ebena (Lea), and quotes this from the Ohio and 

 Wabash. According to Blatchley & Daniels (1903) subrotunda is plentiful in the 

 Wabash and Tippecanoe Rivers in Indiana. The form from Elk River in West 

 Virginia (Big Kanawha-drainage) is slightly dififerent (var. leucogona). Simpson 

 (1900) cites the Cumberland and Tennessee river-systems, and Wilson & Clark 

 (1914) confirm this for the Cumberland. Similar forms are, indeed, found in 

 these rivers, but they generally go under different names (mostly pilaris Lea). 

 Yet I have typical subrotunda from the Tennessee in northern Alabama. Its 

 presence in the Big Sandy in Kentucky has been established. 



All records from outside of this region are to be regarded for the present as 

 doubtful, or positively wrong, as for instance. Grand River, Ontario, and Michigan. 

 The records from Lake Erie given by Sterki (1907o, p. 391) and Ortmann (19096, 

 p. 203) do not refer to this species, but to Pleurobema obliquum pauperculum, and 

 the same probably is true of Walker's record (1913, p. 22). 



Toward the west and southwest, in the Mississippi-drainage, typical subrotunda 

 is gradually replaced by the form or species F. ebena (Lea), which is, for instance, 

 rather prevalent in the Ouachita River in Arkansas. The interrelation between 

 F. subrotunda and F. ebena should be studied more closely especially in the lower 

 Ohio and its tributaries. 



FUSCONAIA SUBROTUNDA KIRTLANDIANA (Lea) (1834). 



Quadrula kirtlandiana (Lea) Simpson, 1914, p. 891. 



Plate I, figs. 3, 4, 5. 

 Records from Pennsylvania: 



Harn, 1891, p. 137 (western Pennsylvania). 



Rhoads, 1899, p. 137 (Beaver River, Wampum, Lawronce Co.). 



Ortmann, 19096, p. 201. 



Characters of variety: Shell with the outline of F. subrotunda, but much more 

 compressed, and with less prominent beaks. The diameter is less than fifty percent 

 of the length, falling as low as thirty-three percent. In consequence of the com- 

 pression, the posterior part of the shell, behind the beaks, appears more elevated, 

 almost wing-like. Color of epidermis generall}^ brighter, chiefly so in young 

 shells, which often possess a very light yellowish ground-color, with darker, well- 

 marked growth-rests, and distinct black or dark green rays. In the old shell. 



