544 ORTMANN— NAYADES OF 



it from Edgemoor, Anderson Go., Tenn., and Pilsbry and Roads give 

 it from Patton's Ferry, Roane Co., Tenn. I also have found it in 

 French Broad River, at Boyd Creek, Sevier Co., Tenn. Records 

 from " Holston River " probably refer to the Tennessee, at any rate, 

 it must be a rare shell above Knoxville. 

 Type locality: Ohio River. 



21. Plethobasus cyphyus (Rafinesque), 1820. 



Obliqnaria cyphya Rafinesque, '20. — Unio cesopus Lewis, '71. — 

 Plethobasus cesopus Ortmann, '12b, p. 260 (anatomy). — Pleuro- 

 hema cesopus Simpson, '14, p. 806. — Pleitrobema cyphia Vanatta, 

 '15. P- 556 



In the larger rivers, Tennessee, Clinch, Powell, Holston, and 

 French Broad, going up, in the Powell, to Bryant Shoals, Claiborne 

 Co., Tenn. ; in the Clinch to Clinchport, Scott Co., Va. ; in the Hol- 

 ston to the mouth of the North Fork at Rotherwood, Hawkins Co., 

 Tenn. 



Type locality: Falls of the Ohio. 



22. Plethobasus cyphyus compertus (Frierson), 191 1. 



Unio varicosus Lewis, '71. — Unio compertus Frierson, '11, p. 53, pi. 



3 (middle and lower figures). — Pleurobema compertum Simpson, 



'14, p. 809. 



Specimens in the Walker collection from " Holston River, Knox- 

 ville," are authentically labeled varicosus Lewis, and compertus 

 Frierson, and they agree very well with specimens collected by my- 

 self in French Broad River, at Boyd Creek, Sevier Co., Tenn. My 

 specimens (I have five) are larger than Frierson's figures, and 

 most of them are more drawn out posteriorly. They were found as- 

 sociated with one specimen of the true P. cyphyus, and resemble the 

 latter very much, except that the radial row of knobs on the disk 

 is poorly developed, almost obliterated, and that the soft parts are 

 not of orange, but of pale color. (For the rest, the anatomy of male 

 and female is like that of P. cyphyus.) 



I consider this as a variety of P. cy[^hyus, since in some of my 

 specimens, the row of knobs is more distinct, and since typical 



