UPPER TENNESSEE DRAINAGE. 583 



Distinguished by the distinct and sharp posterior ridge, depressed 

 (truncated) posterior slope, and the peculiar, wedge-shaped anterior 

 part of the shell. But these characters gradually pass into those of 

 the variety ventricosa. 



The typical L. ovata is restricted to the larger rivers, and quite 

 abundant there. It is in the Tennessee, the Little Tennessee, Hol- 

 ston. Clinch, and Powell. In the Powell, it goes up to Shawanee, 

 Claiborne Co., Tenn. ; in the Clinch, to Clinchport, Scott Co., Va. It 

 is the prevailing form in the Holston proper, but does not go into the 

 Forks of the Holston. All along its range, and chiefly above Knox- 

 ville, it is accompanied by the var. ventricosa, and intergrades with 

 it. But at the points just named, it disappears, and leaves the field 

 to ventricosa. 



Type locality: Ohio River. 



72. Lampsilis ovata ventricosa (Barnes), 1823. 



Unio ventricosa Barnes, '23. — Lampsilis ventricosa Ortmann, '12&, 

 p. 351 (anatomy). — Lampsilis ovata ventricosa Ortmann, '13&, p. 

 311. — Lampsilis ovata ventricosa Goodrich, '13, p. 95. — Lampsilis 

 ventricosa Simpson, '14, p. 38. 



According to Vanatta ('15, p. 551), the type of Lampsilis car- 

 dium Rafinesque, '20, is this, and also Conrad ('34) says so. How- 

 ever, this conflicts with Rafinesque's description, from which it is 

 evident that L. cardium is the female of L. ovata. We have here a 

 case where the " type " does not agree with the original description, 

 and it should be borne in mind that the co-called " types " of Rafin- 

 esque, in the Philadelphia Academy, are not types in the strict sense, 

 but merely " authentic specimens " of somewhat doubtful value. 



In this variety, the posterior ridge becomes indistinct, the pos- 

 terior slope is not excavated, and the anterior part of the shell is not 

 remarkably compressed. Also, the shell is generally less convex. 

 But there are all stages of transition. The upper Tennessee form of 

 ventricosa very rarely has the distinct rays of the corresponding 

 form of the upper Ohio region. 



L. ovata ventricosa is found associated with the normal L. ovata 

 in the larger rivers, but is less frequent there. It goes, however, 



