538 ORTMANN— NAYADES OF 



according to actual measurements, should be classed with tiunescens. 

 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 tumesceiis-iorm 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 bigbyeusis-iorm is in the smallest streams. Forms be- 

 longing to the latter, corresponding closely to fassinaiis rhoinboideiiiii, 

 and the large estabrookiamts-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 

 baj'uesiana prevailing. 



Genus: Amblema Rafinesque, 1820. 



Crenodonta (Schlueter, '36), Ortmann, igi2b, p. 245. — Amblema 

 Frierson, I9i4a_, p. 7. 



12. Amblema plicata costata (Rafinesque), 1820. 



Ambletna costata Rafinesque, '20. — Unio nndnlatus Lewis, '71. — 

 Unio nndnlatus Pilsbry & Rhoads, '96. — Crenodonta uiidulata 

 Ortmann, '12b, p. 246 (anatomy). — Crenodonta nndidata Good- 

 rich, '13, p. 93. — Qiiadrula undulata Simpson, '14, p. 819. — 

 Amblema costata Frierson, '14a, p. 7. — Onadrnla costata Vanatta, 

 '15, p. 556. — 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 



