﻿] 24 I.AMl'SII.lS 



slightly ])ro{luce(l at the anterior base, and occasionall)' straij2:ht 

 on the basal line. All the female shells seen are smaller than 

 the males ; they are shaped much like those of the males but 

 are a little fuller at the. post-base. 



Length (male) 52, height 30, diam. 19 mm. 



Length (female) 38, height 23, diam. 14 mm. 



Cumberland and Tennessee River systems ; Othcalooga 

 Creek, northwest Georgia. 



Type locality, Cumberland River, Tenn. 

 Margarita (Unio) siinus Lea, Syn., 1836, p. 29; 1838, p. 21. 

 Unio simus Lea, Tr. Am. Phil. Soc, VL 1838, p. 26, pi. viii, 



fig. 20; Obs., H, 1838, p. 26, pi. VIII, fig. 20. — Chenu, 111. 



Conch., 1858, pi. XXI, figs. 4, 4a, 4/7. — KusTER, Conch., Cab. 



Unio, 1861, p. 248, pi. Lxxxiii, fig. 4; p. 262, pi. Lxxxviii, 



%• 3- 

 Margaron (Unio) simi4^ Lea, Syn., 1852, p. 31 ; 1870, p. 50. 

 Lampsilis simus Simpson, Syn., 1900, p. 556. 

 Unio notatus Conrad, Pr. Ac. N. Sci. Phila., VI, 1853, p. 253. 

 Unio spatulatus Sowerby, Conch. Icon., X\'I, 1868, pi. lxv, 



fig. 328. 

 f Unio proximus Kuster, Conch. Cab. Unio, 1861, p. 248, pi. 



LXXXIII, fig. 4. 



This species seems to combine characters of the eUipsiformis 

 and the iris groups. Its solidity and form are characters of the 

 former group, though the young shells are shaped like young 

 ncbniosa, while the beak sculpture and color pattern are those 

 of the iris group. 



Lampsilis planca (Lea). 



Shell irregularly obovate, subinflated, subsolid. with a well- 

 developed, somewhat rounded posterior ridge ; beaks rather 

 full but not hig'h, their sculpture not seen ; surface rather 

 smooth and shining, dirty greenish-yellow or dirty tawny, with 

 a few wide or narrow, faint, often broken rays ; left valve with- 

 two small, stumpy pseudocardinals and two short laterals ; 

 right valve with one pseudocardinal, sometimes with a vestige 

 of one above it, and one lateral ; muscle scars well marked ; 

 beak cavities shallow ; nacre bluish-white, lurid in the center. 



