538 ORTMANN—NAYADES OF 
according to actual measurements, should be classed with tumescens. 
But these shells are more or less distorted and stunted, and appar- 
ently abnormal; those of more normal growth correspond in their 
measurements to barnesiana., 
Type locality: “ Alexandria, La.” This is surely incorrect. 
Specimens from the Tennessee River in northern Alabama have 
been recognized as this form by Call, Pilsbry and Rhoads, and Walker ; 
and Lewis (’72), and Pilsbry and Rhoads quote it from East Ten- 
nessee, and I think this identification is quite correct. 
Note: In northern Alabama, in the Tennessee drainage, and gen- 
erally below the Walden Gorge, this type of shell is also abundant, 
and again here we have the twmescens-form in the Tennessee proper 
and the lower parts of some of the tributaries (Sequatchie River, 
Shoals Creek). Farther up in the tributaries, typical barnesiana pre- 
vails, and the bigbyensis-form is in the smallest streams. Forms be- 
longing to the latter, corresponding closely to fassinans rhomboideum, 
and the large estabrookianus-type of the upper Powell, Clinch and 
Holston, have come to hand from the headwaters of Paint Rock 
River and Elk River (Estill Springs). In Shoals Creek, Lauder- 
dale Co., Ala., a very peculiar mixture is found, containing all three 
types side by side, intergrading completely, but with the typical 
barnesiana prevailing. 
Genus: AMBLEMA Rafinesque, 1820. 
Crenodonta (Schlueter, °36), Ortmann, 1912), p. 245——Amblema 
Frierson, 19144, p. 7. 
12. AMBLEMA PLICATA COSTATA (Rafinesque), 1820. 
Amblema costata Rafinesque, ’20—Unio undulatus Lewis, ’71.— 
Unio undulatus Pilsbry & Rhoads, ’96.—Crenodonta undulata 
Ortmann, *12), p. 246 (anatomy ).—Crenodonta undulata Good- 
rich, °13, p. 93—Quadrula undulata Simpson, *14, p. 819.— 
Amblema costata Frierson, ’14a, p.7.—Quadrula costata Vanatta, 
"15, p- 550.—Amblema (plicata) costata, Utterback, ’16, p. 39. 
As to nomenclature, see Frierson and Vanatta (/. c.). The iden- 
tity of Raflnesque’s species has been recognized already by Conrad in 
