792 PLEUROBEMA 
Unio tibulcides Lata, Pr. Ac. N. Sci. Phila., III, 1859, p. 154; 
Jl. Ac N.Sei: Philas VV,:1850; poe to pl: xexvinehie toe; 
Obs., VII, 1859, p. 37, pl. Xxvu, fig. 100 —Sowerrpgy, Conch. 
Icon., X V1, 1866, pl. x11, fie. 223: 
Margaron (Unio) fibuloides Lea, Syn., 1870, p. 56. 
Very close to irrasum, but shorter, rather more nearly round, 
solider and having a more tawny epidermis. Conrad’s Unio 
altus is apparently a light-colored young shell, having a ray 
on each valve broken into squarish spots. 
PLEUROBEMA HARTMANIANUM (Lea). 
Shell almost triangular, inequilateral, inflated, solid; beaks. 
full and high, turned a little forward; anterior end generally 
obliquely truncate above, rounded below; base line slightly 
curved; outline of dorsal slope curved, elevated to a low angle 
behind the ligament; posterior ridge well developed, angled 
above, somewhat double below, ending near the base in a bian- 
gulation; surface rudely and unevenly concentrically sculp- 
tured, epidermis tawny to tawny-brown; pseudocardinals rag- 
ved, two in the left valve, three in the right; laterals strong, 
two in the left valve and a double one in the right; beak cav- 
ities shallow, compressed; muscle scars small, deep; nacre 
white, thinner and iridescent behind. 
Length 50, height 51, diam. 35 mm. 
Coosa River, Alabama. 
‘Type locality, Coosa River, Wetumpka, Ala. 
Unio haritmanmianus Lea, Pr. Ac. N. Sci. Phila., IV, 1860, p. 
307.> Jl, Ac. Nu Scis Phila, Vji862, p.73;, ple wan; fie ear 
Obs., VI, 1862)'p.'77; pl; vant, Hes 222: 
Margaron (Unio) hartmanianus Lea, Syn., 1870, p. 38. 
Pleurobema hartmaniana Simpson, Syn., 1900, p. 756. 
Close to taitianwm, but not so high, the outline being near to 
an equilateral triangle while that of faitianwm is an inequilat- 
eral triangle. ‘There are, however, intermediates, which hint 
strongly at a connection of the two. The two forms differ 
pretty constantly from P. cor in having a decided posterior 
ridge, in front of which the disk is flattened. In cor the pos- 
