﻿54 I.AMl'SIMS 



but solid when the shell is adult; the posterior is triang-ular ; 

 tlicre are two strong laterals, the lower the heavier; the hinge 

 line is rounded and narrow in the middle ; right valve with a 

 heavy pseudocardinal, with a small tooth often l>ehind it and 

 a compressed small one above it ; there is a single, strong, trun- 

 cate lateral ; beak cavities moderately deep ; muscle scars well 

 impressed, smooth; nacre whitish, often salmon in the center 

 of the shell. The female shell is not greatly inflated at the 

 posterior region. 



Length 85, height 55, diam. 40 mm. 

 Length 65, height 45, diam. 30 mm. 



Type locahty, Williamsport, Tennessee ; also near Columbus, 



Mississippi; Cahawba and lUack Warrior Rivers, Alabama. 



Unio clarkianiis Lea, Pr. Am. Phil. Soc, V, 1852, p. 251 ; Tr. 



Am. Phil. Soc, X, 1852, p. 273, pi. xxi, fig. 30; Obs., V, 



1852, p. 29, pi. XXI, fig. 30. 



Margaron (Unio) darkianus Le^a, Syn., 1852. p. 27 ; 1870, p. 



42. 

 Lampsilis clarkianiis Simtson, Syn., 1900, p. 532. 

 Unio spillmanii Lea, Pr. Ac. N. Sci. Phila., XIII, 1861, p. 39; 

 Jl. Acad. N. Sci. Phila., V, 1862, p. 98, pi. xv, fig. 246; Obs., 

 VIII, 1862, p. 102, pi. XV, fig. 246. 

 Margaron (Unio) spillmanii Lea, Syn., 1870, p. 42. 



When fully matured this has one of the most solid shells of 

 any species in the group. Even the young shells are quite 

 heavy. This solidity, its heavy teeth and the peculiar waxy 

 texture of the shell are its best distinguishing characters. I 

 believe it to be absolutely identical with the Unio spillmanii of 

 Lea. The 'habitat "Williamsport, Tennessee," given by Lea, 

 is open to doubt. He also gives Georgia or Alabama on the 

 authority of Wlieatley and it is found in both of these states. 



L-^^MPsii.is GERHARirrii (Lea). 



Shell subrhomboid, but slightly inflated, subsolid, with only 

 moderately high beaks ; there is a rather long ligament, which 

 runs forward under the beaks and is embedded in front of 

 them in a narrow lunule ; posterior ridge well developed. 



