﻿PI.AGIOLA -JO7 



ri.AGioi.A Ei.cGANs (Lea). 



Shell subrhomboid, solid, inflated, with a very sharp pos- 

 terior ridge, behind which it is decidedly truncated; beaks 

 high and full, turned forward over a small lunule ; region of 

 the beaks and upper part of the shell decidedly flattened; 

 central base of the shell full; posterior point sharp, elevated 

 considerably above the base; surface with irregular, subsul- 

 cate growth lines ; epidermis dull or somewhat shining, often 

 having wrinkled loops behind, yellowish-green with numerous 

 wavy, often broken, rays. Sometimes in addition to the rays 

 there are numerous wavy or zigzag lines and occasionally the 

 shell is tawny or reddish and rayless ; hinge line curved ; pseu- 

 docardinals ragged, two in the right valve and one in the left, 

 sometimes they are much split up ; left valve with two laterals ; 

 right valve with one and sometimes a faint second one below 

 it; beak cavities not deep; muscle scars impressed; nacre 

 bluish-white, white, salmon or reddish. The form of the shell 

 is quite variable and those of the female and male differ but 

 little from each other. The female shell is a little more pro- 

 duced at the central base. 



Length (male) 57, height 43, diam 30 mm. 



Length (female) 68, height 52, diam. -7,7 mm. 



Mississippi drainage generally; Michigan; Lake Michig-an ; 

 southwest to Trinity River, Texas. 



Type locality, Ohio River. 

 Vnlo dedans Li-a, Tr. Am. Phil. Soc, I\;, 1831, p. 83, pi. ix, 



fig. 13; Obs., L 1834, p. 93, pi. IX, fig. 13.— Hanley, Biv, 



Shells, 1843. P- 183, pi. XXI, fig. 33.— Chenu, 111. Conch., 



1858, pi. XV, figs. 3. 30, 3^ ; Manual, IL 1859, p. 138, fig. 6'j2. 



— SowERBY, Conch. Icon., XVI, 1868, pi. i,xxiv, p. 380. 

 Margarita (Unio) elegans Lea, Syn., 1836, p. 18; 1838, p. 16. 

 Margaron (Unio) elegans Lea, Syn., 1852. p. 23 ; 1870, p. 36. 

 Plagiola elegans Baker, Moll. Chicago, Pt. i. 1898, p. 91, pi. 



xxi, fig. I. — Simpson, Syn., 1900, p. 604. 

 Amygdalonajas elegans Ortmann. Ann. Car. Mus., VIIL 



1912, p. 328. 



