570 ORTMANN— NAYADES OF 



be this species. However, I hesitate to accept this, till it has been 

 shown that this species actually exists in Greene River. 



N. pectorosa is found in the Tennessee below and at Knoxville 

 (Lewis, Pilsbry & Rhoads), but it seems to be rare there. Farther 

 up, it goes into Clinch, Powell, Holston, French Broad, and lower 

 Nolichucky, and it is also in Little River. It ascends toward the 

 headwaters farther than does A^. ligaiiientina gibha, and goes, in the 

 Powell, to Pennington Gap, Lee Co., Va. ; in the Clinch to Cleve- 

 land, Russell Co., Va. ; in North Fork Holston, to Saltville, Smyth 

 Co., Va. ; in South Fork Holston, to Barron, Washington Co., X'a. ; 

 and in the Watauga, to Watauga, Carter Co., Tenn. Just in the 

 region, where N. ligamentina gibha begins to disappear (north of 

 the Va.-Tenn. state line), N. pectorosa is most abundant and in its 

 best development. 



Type locality: Elk River, North Alabama. 



Genus: Amygdalonaias Fischer & Crosse (1893). 

 Ortmann, '12b, p. 327. 



56. Amygdalonaias TRUNCATA (Rafinesque), 1820. 



Truncilla tnincata Rafinesque, '20. — Unio elegans Lewis, '71. — 

 Amygdalonaias elegans Ortmann, '12b, p. 328 (anatomy). — 

 Plagiola {Amygdalonaias) elegans Simpson, '14, p. 307. — 

 Plagiola elegans Vanatta, '15, p. 553. — Amygdalonaias truncata 

 Utterback, '16, p. 148. 



Vanatta does not accept Rafinesque's specific name on account of 

 Unio truncata Spengler, 1793. However, these do not conflict 

 (Walker, '16). 



Not abundant, and missing in the headwaters. Tennessee below 

 Knoxville (Lewis); Clinch River, Solway, Knox Co.; Edgemoor 

 and Clinton, Anderson Co. ; Black Fox Ford, Union Co. ; Clinch 

 River Station, Claiborne Co. ; Oakman, Grainger Co., Tenn. Hol- 

 ston River, McBee Ford, near Hodges, Jefferson Co., Tenn. 



Type locality: Ohio River (type from Falls of the Ohio, accord- 

 ing to Vanatta). 



