714 UNIO 
exact miniatures of the larger U. obesus. Occasionally the 
anterior end is considerably narrowed and the posterior ridge 
becomes somewhat double. I have found such specimens in 
Manatee County, Florida. 
UNIO BISSELLIANUS Lea. 
Shell long rhomboid, subsolid or solid, subinflated, inequi- 
lateral; beaks somewhat elevated, moderately full, their sculp- 
ture a few strong ridges that curve up decidedly behind ; pos- 
terior ridge full, rounded, sometimes having above it a couple 
of low, radiating ridges; dorsal slope decidedly obliquely 
truncated ; base line nearly straight ; dorsal line curved a little; 
anterior end rounded; surface with concentric growth lines; 
epidermis dull greenish, concentrically wrinkled, usually 
slightly rayed, having a broad faint ray on the posterior ridge 
and two narrower ones above it; pseudocardinals subcom- 
pressed, two in the left valve and one in the right; laterals 
curved; muscle scars shallow; nacre having a lurid purplish 
tint, iridescent behind. 
Length 70, height 40, diam. 22 mm. 
Type locality, Bissel’s Pond, Charlotte, North Carolina. 
Unio bisselianus Lra, Pr. AGN. Sci. Phila. Xe 1867, p. S15 
jt. Ac. N.; Sei. Phila, V1, 2868.9) 277. plo xevin ie oo, 
Obs., XII, 1860, p. 37, pl. xxxvu, fig. 90.—Simpson, Syn., 
1900, p. 743. 
Margaron (Unie) bisselianus Lea, Syn., 1890, p. 50. 
Close to forms of U. obesius, but the epidermis is colder, not 
so rough and is rayed behind. I have before me a shell said 
to come from Lucile, Lauderdale County, Mississippi, received 
from Mr. Berlin H. Wright, which approaches U. bissellianus 
more nearly than anything, but I do not feel safe in referring 
it to that. 
Section Mrcronatas Simpson, 1900. 
Micronaias SIMPSON, Syn., 1900, p. 743. 
Shell small, oval, a little produced near the posterior base, 
with a moderate posterior ridge and pointed near the base be- 
hind: beaks rather prominent, the sculpture being apparently 
