QUADRULA 873 
Margarita (Unio) rubiginosus Lia, Syn., 1836, p. 20; 1838, 
pot: 
Margaron (Unio) rubiginosus Lia, Syn., 1852, p. 24; 1870, 
P- 37: 
Unio rubiginosa Dresuayes, An. sans Vert., 3d ed., II, 1839, 
pr 672. 
Quadrula rubiginosa BAKER, Moll. Chicaco, Pt. 1, 1898, p. 77, 
pl. x1x, fig. 2; xx, fig. 1-——Simpson, Syn., Igoo, p. 786. 
Fusconaja rubiginosa ORTMANN, Ann. Car. Mus., VIII, 1912, 
Dp. 241, figs. 4-4a. 
Unio flavus Conran, Monog., IX, 1837, p. 74, pl. xi, fig. 2.— 
Koster. Conch. Cab), 1852, p. 61, pl. xiv, fig. 25 p: 265, pl. 
EGR Ms fe. 15. 
Unio flavus var. rubiginosus Pater, Conch. Sam., IIT, 1890, 
p- 152. 
Unio trigonus Sowerby, Conch. Icon., XVI, 1868, pl. LXIv, p. 
322. ; 
This is a very abundant, widespread and variable species. 
Some specimens are compressed and long rhomboid, of rather 
light structure. Others are subtriangular, inflated, solid and 
approach so close to undata that it is a question to which spe- 
cies they should be assigned. It is also close to cerina, so much 
so that Dr. Lea believed the latter to be synonymous. It is 
less strongly sculptured than rubida and does not have the pe- 
culiar reddish tint commonly found in that species. It is more 
rude than cerina, it is not so richly or darkly colored and it 
lacks the rest marks often found in that species. 
QUADRULA CERINA (Conrad). 
Shell. rhomboid, convex to subinflated, subsolid, inequilat- 
eral; beaks somewhat full and high; posterior ridge well de- 
veloped, subangular, often slightly double below, ending in a 
feeble biangulation at the base of the shell; anterior end 
rounded; base line straight or lightly curved; outline of dor- 
sal slope raised to an angle in the middle, obliquely truncate 
below; surface with faint, uneven, concentric sculpture; epi- 
dermis brownish to reddish-brown, generally showing feeble 
