“J 
UNIO 58 
Group of Unio coloratus. 
Shell somewhat rhomboid, solid, slightly biangulate behind, 
rather compressed, more or less sculptured with concentric 
sulcations; beaks moderately prominent, their sculpture un- 
known ; epidermis brownish; teeth strong; laterals rather club- 
shaped ; nacre white or purple. Animal unknown. 
Unto cororaAtus Charpentier. 
Shell subrhomboid, convex, solid, densely sculptured with 
fine striations ; epidermis brownish-olive ; beaks rather full, pos- 
terior ridge moderate, scarcely double, ending in a feeble bian- 
gulation near the base; pseudocardinals thick, serrated; nacre 
dark purple, shining. 
Medellin River, Vera Cruz, Mexico. 
Unio coloratus CHARPENTIER, in Kuster, Conch. Cab. Unio, 
1856, p. 155, pl. xiv, fig. 6 —StmMpson, Syn., 1900, p. 700. 
Unio cuprinus var. coloratus, VON MARTENS, Biol. Cent. Amer., 
Moll., 1900, p. 506. 
I am strongly inclined to believe that this and Lea's Unio 
callosus are identical. The figures show Charpentier’s shell to 
be a little straighter than Lea’s on the base, otherwise the out- 
lines and figures agree very closely. Both authors claim that 
their shells are compressed, but the outline figures of dorsal 
views show them to be quite convex. l[ea’s shell has white 
nacre while that of Charpentier’s is dark purple, but this is 
often a difference of no importance, for the same thing occurs 
in Unio complanatus, U. buckleyi, Tritogonia tuberculata and 
many other species. I have seen a single specimen belonging 
to Mr. Berlin H. Wright, which I was inclined to refer to this 
species, though it did not fully agree with the description and 
figure. 
UnNIo cALLosus Lea. 
Shell rhomboid elliptical, convex, solid, inequilateral with a 
moderate, feebly biangulate posterior ridge, which terminates 
behind a short distance above the basal line; beaks somewhat 
prominent but eroded in the type; epidermis yellowish-brown. 
