542 ORTMANN— NAYADES OF 



It is remarkable that I did not find it in the lower parts of these 

 rivers, although it has been reported from the Knoxville region, and 

 from the Tennessee in northern Alabama. 



Type locality: Nolichucky River, Tenn. 



17. OUADRULA CYLINDRICA (Say), 1817. 



Unio cylindricus Say, '17. — Unio cylindricus Lewis, '71. — Unio cylin- 

 driciis Pilsbry & Rhoads, '96. — Quadrula cylindrica Ortmann, 

 12b, p. 256 (anatomy). — Quadrula cylindrica Simpson, '14, p. 

 832. 



Reported from the Tennessee below Knoxville and from the 

 Holston River. It is rather frequent in the larger rivers, and goes, 

 in the Holston, up to Hawkins Co., Tenn. In the region of the forks 

 it begins to incline toward the next form ; however, in Big Mocassin 

 Creek, Mocassin Gap, Scott Co., A'a., a tributary of the North Fork, 

 I found a rather normal cylindrica. In the Clinch, it goes to Clinch- 

 port, Scott Co., \"a. It is also in the Powell, up to Claiborne Co., 

 Tenn. 



Type locality: Wabash River. 



18. Quadrula CYLINDRICA STRiGiLLATA (Wright), 1898. 



Unio cylindricus strigillatus Wright, Nautilus, 12, '98, p. 6. — Quad- 

 rula cylindrica strigillata Ortmann, '13&, p. 31.1. — Quadrula cylin- 

 drica strigillata Goodrich, '13, p. 93. 



Simpson ('14, p. 834) does not admit this as a separate form; 

 but it is a very good and well-marked local race, belonging to the 

 headwaters, being compressed, devoid of large tubercles, but thickly 

 covered with small ones. 



Its metropohs is in the upper Clinch River. Intergrades between 

 this and the main form are found in Scott Co., Va., and thence far- 

 ther up, it becomes a pure race, and goes up to Cedar Bluff in Taze- 

 well Co., Va. The same conditions prevail in Powell River, where 

 it intergrades with the normal type in Claiborne Co., Tenn., and then 

 goes up to Pennington Gap in Lee Co. It also exists in North Fork 

 Holston. from Hawkins Co., Tenn., to Mendoto, Washington Co., 

 Va., and in the South Fork Holston at Pactolus, Sullivan Co., Tenn. 



