﻿OBOVARIA 301 



Unio castanciis Lka, Tr. .\m. Phil. Soc, IV, 1831, p. 91, pi. xi, 



fig. 21 ; Obs., I, 1834, p. loi, pi. XI, fig. 21. — Hanley, Biv. 



Shells, 1843, P- i88» Pl- xxii, fig. 30. — Chenu, 111. Conch., 



1858, pi. XI, figs. 5, 5a, 5^^. 

 Margarita (Unio) castaneus Lea, Syn., 1836, p. 22 ; 1838, p. 18. 

 Margaron (Unio) costonens Lea. Syn., 1852, p. 26; 1870, p. 41, 

 Obovaria castanea SijMpson, Syn., iqoo, p. 602. 



Much smaller and darker than ellipsis, and the difference 

 between male and female shells is much more strongly marked. 

 Some of the male shells approach closely to Lea's Unio simu- 

 lans, but are generally a little heavier and more inflated. In 

 the latter species the male and female shells are essentially 

 alike. 



The name castaneivs was applied to some Unio, which I am 

 unable to determine, by Rafinesque in a Continuation of a Mon- 

 ograph on the Bivalve Shells of the River Ohio, etc., in Octo- 

 ber, 183 1. According to Scudder, Lea's name was published the 

 latter part of the same year, but I have no means of knowing 

 which appeared first. Under the circumstances I use Lea's 

 name. 



Obovaria jacksoniana Frierson. 



"Shell ovate, smooth, rounded before and below, nearly 

 straight from beak to post-point, which is about half way the 

 height of the shell ; umbonal ridge low, and the posterior area 

 very narrow ; beaks not high, sculpture not seen ; nacre bluish- 

 white, iridescent behind : teeth double in left, single in right 

 valve ; cardinals stout, erect ; laterals not very large ; muscle 

 scars confluent behind, separate before ; pallial line obsolete 

 behind. 



Length 45, height 33, diam. 20 mm." (Frierson). 



Type locality. Pearl River, Mississippi. Also in the Yala- 

 busha River, Mississippi. 

 Unio (Obovaria) jacksoniamis Frierson, Naut. XXVL 1912, 



p. 23, pi. III. figs. I, 2, 3. 



"The novelty of the present species was determined by gra- 

 vid specimens collected by Mr. A. A. Hinkley and by a com- 

 parison with castaneus of the Lea collection by Mr. Bryant 



