530 ORTMANN— NAYADES OF 



state line, in Virginia, it is exclusively present, going up to Big Stone 

 Gap, entering even a small tributary (Cane Creek, Lee Co., Va.). 



In the Holston, this form is not so well developed, and not so 

 abundant, but is present nevertheless, and also has the same relation 

 to lesueuriana, first being associated with it, but then being exclusively 

 present. The latter is the case in North Fork Holston, in Washing- 

 ton Co., Va. In South Fork Holston, it goes up to Blufif City, Sulli- 

 van Co., Tenn., but accompanied by lesueuriana; but it enters here 

 Wautauga River, where it is found alone. In the Holston proper, in 

 a downstream direction, it is quite rare, but it has been found as far 

 down as Grainger Co., so that in this region (as is the case in lower 

 Clinch) occasionally all three forms of the species may be obtained 

 together. 



Type locality: Powell River, Va. (topotypes examined). 



Note: The color of the soft parts and eggs in the pilaris group 

 varies greatly. The soft parts may be of the orange type, and the 

 eggs (and placentae) may be red: this is chiefly the case in Powell 

 and upper Clinch rivers. Elsewhere, in Holston, French Broad, and 

 Tennessee, pale soft parts, with whitish eggs prevail. 



5. FuscoNAiA cuNEOLus (Lea), 1840. 



Unio cuncolus Lea, '40. — Unio cuneatus Reeve, Conch. Icon. 16. 

 Unio, '64, pi. 16, f. 73. — Unio cuncolus Lewis, '71. — Unio cunc- 

 olus Pilsbry & Rhoads, '96. — Plcurobeiiia cuncolus Simpson, '14, 

 P- 743- 



This is not a Pleurobeina, but a Fusconaia, taking the place of the 

 group of F. flava (Raf.) (=rubiginosa Lea) in the upper Tennessee 

 region. It is a very good species. 



The original and typical cuncolus represents a compressed head- 

 waters-form, which, farther down, changes into a more swollen 

 form. I have, arbitrarily, decided to call specimens with the diameter 

 less than 50 per cent, of the length by this name. 



This form is found in Powell, Clinch, and Holston rivers, in the 

 upper parts. In the Powell, from L'nion Co., Tenn., up to dinger, 

 Lee Co., Va. (also in Puckcll Creek, Lee Co.) ; in the Clinch from 

 Anderson Co., Tenn., up to Clinchport, Scott Co., Va. ; in the Holston 



