886 QUADRULA 
Margarita (Unio) solidus Lea, Syn., 1836, p. 20; 1838, p. 17. 
Margaron (Umo) solidus lea, Syn., 1852, p. 25; 1870, p. 38. 
Quadrula solida StMpPson, Syn., 1g00, p. 789. 
?Unio cardiacea DesHAyes, Tr. Elem. de Conch., 1839, p. 19, 
pla xx xt ess te2: : 
Unio fulgidus Lea, Pr. Am. Phil. Soc., IV, 1845, p. 164; Tr. 
Am. Phil. Soc, X, 1848, px 735pl: iv, fis-.105 Obs:, WWE 348 
p47, play, fig 10: 
Margaron (Unio) fulgidus Lea, Syn., 1852, p. 25; 1870, p. 38- 
Unio obovalis Conran, Pr. Ac. N. Sci. Phila., VI, 1853; p. 253. 
It is almost impossible to draw up a description that will 
characterize all the variations of this protean species and sepa- 
rate it from the other closely allied forms. Generally its out- 
line approaches that of a right-angled triangle, the beaks being 
full, high and piaced far forward. ‘The anterior end is ordi- 
narily truncated, sometimes squarely, occasionally falling back 
a little above. The base line is nearly straight; the post-dorsal 
outline is lightly curved; the posterior ridge is low and nearly 
straight. Although the shell has its greatest diameter in front 
of the middle there is scarcely any depression between this 
inflation and the posterior ridge as there is in plena, undata, 
obliqua and many specimens of pyramidata. 
I have seen numerous old shells, which are much lengthened 
at the posterior base, with high beaks placed far forward that 
I have been unable to satisfactorily name. One of these is in 
the Lea collection and Dr. Lea calls it Unio solidus. 1 cannot 
be sure whether he is right or wrong. 
QUADRULA PLUNA (Lea). 
Shell short and high, subtriangular, inflated, inequilateral, 
solid; beaks very full and high, turned forward over a deep, 
ragged lunule, sculptured with a few irregular nodulous ridges ; 
anterior end strongly and obliquely truncated, the truncation 
often developed into a second lunule; base line short, straight 
or lightly sinused in front of the posterior ridge; outline of 
dorsal slope curved; posterior ridge narrowly rounded, curved, 
ending at the base in a blunt point; median radial ridge full 
