828 QUADRULA 
Unio nicklinianus Lua, Tr. Am. Phil. Soc., V, 1834, p. 28, pl. 
1, fig. 1; Obs., 1, 1834, p. 140, pl. 1, ig. 1—HaNLEy, Biv. 
Shells, 1543, p. 175, pl. XXI, hg. 52.—SoweERBy, Conch. Icon., 
AV 1 1666, pl rau, e270: 
Margarita (Unio) mckunianus Lea, Syn., 1836, p. 12; 1838, 
De EA: 
Margaron (Umo) mcklinianus Lua, Syn., 1852, p. 19; 1870, 
Dp. 28. 
Plectomerus nicklinianus Conran, Pr. Ac. N. Sci. Phila., VI, 
1853, p. 261. 
Quadrula nickliniana SIMPSON, Syn., 1900, p. 771. 
Unio nicklianus Kustrr, Conch. Cab., 1861, p. 218, pl. Lxxrt, 
fig's:3: 
Shorter than Q. stolli, having a more elaborate pattern of 
sculpture and usually a sort of hump on the middle of the 
lower posterior ridge. I am able to separate Lea’s shells, 
which he calls Unio nicklinianus, into two lots, one agreeing 
with his type, the other longer and answering very well to the 
description and figure of Unio stolli von Martens. 
QUADRULA STOLLI (von Martens). 
Shell subtrapezoid, compressed, solid, quite inequilateral ; 
beaks compressed and rather low; dorsal line nearly straight, 
produced into a gradually expanding wing behind; posterior 
slope with a long oblique truncation, angled above, rounded 
below ; base line nearly straight; anterior end somewhat nar- 
nowed and rounded, angled a little below the beaks; surface 
covered with low, radiating, somewhat corrugated or broken 
folds, whose radius is below the beaks and which spread out 
behind in light curves; there is also moderate concentric sculp- 
ture; pseudocardinals strong, radial, rough, two in the left 
valve and three in the right; laterals heavy, remote, two in the 
left valve and one in the right ; beak cavities deep, compressed ; 
muscle scars large, the anterior nearly filled with roughened 
matter; nacre white, much thicker in front; pallial line re- 
mote. 
Length 160, height over all 120, diam. 40 mm. 
Rio de las Salinas, Guatemala; Moctezuma River, Central 
America? 
