710 UNIO 
rounded, ending behind in a blunt point at or very near the 
base of the shell: base line incurved a little in the middle ; dor- 
sal line nearly parallel with the base line; anterior end rounded ; 
posterior end obliquely subtruncated, the outline being some- 
what curved, meeting the dorsal line with a sharper curve; 
surface finely, concentrically striate; epidermis finely, concen- 
trically wrinkled, becoming cloth-like around the border of the 
shell, smoother on the disk, greenish-brown to reddish-brown ; 
pseudocardinals stumpy, quite solid, rough, two in the left 
valve and one in the right; laterals remote, somewhat club- 
shaped: muscle scars shallow, anterior separate, posterior 
large; nacre whitish, often tinted with lurid purple. 
Length &8, height 44, diam. 28 mm. 
Length 70, height 39, diam. 21 mm. 
Chattahoochee River, Georgia, west to Little Patsaliga Creek, 
Alabama. 
Type locality, Creeks, Columbus, Ga. 
Umo columbensis Wea, Pr Aco N.Sct Phila; xs 1657, pase; 
JimAcoNS Sct Phila, PVs 18585 p.75, "pl. iv; tie 5c Obs 
VI, 1858, p. 75, pl. xiv, fig. 55 SIMPSON, Syn., 1900, p. 741. 
Margaron (Umo) columbensis L¥a, Syn., 1870, p. 50. 
Unio columbiensis Parrri, Conch. Sam., HI, 1890, p. 148. 
Exceedingly close to forms of U. tetralasmus on the one 
hand and U. obesu 
a 
on the other. It is generally a solider 
shell than either, its teeth are normally considerably heavier 
and it differs a little from either in texture in an almost in- 
describable way. Its color is colder, not so warm and soft as 
that of tetralasiius or obesus. 
UNIo ospesus Lea. 
Shell rhomboid, subinflated or inflated, subsolid, inequilat- 
eral; beaks full, high, their sculpture numerous ridges which 
are strongly curved up behind; posterior ridge high, rounded, 
ending in a point, rarely a feeble biangulation at or very near 
the base of the shell; posterior slope with two faint, radial 
sulci, obliquely truncated; surface with irregular growth 
lines; epidermis tawny-brown to dark brown, longitudinally 
wrinkled, often cloth-like; pseudocardinals generally small, 
