706 UNIO 
Margaron (Unio) symmetricus LEA, Syn., 1852, p. 32; 1870, p. 
7. 
Unio porrectus Conrab, Jl. Ac. N. Sci. Phila., 1854, p. 296, pl. 
MMVI OIL 72 ; 
Unio subcroceus CONRAD, Jl. Ac. N. Sci. Phila., VII, 1854, p. 
2077) ple xvils fis: FLL 
Unio jamesianus Lea, Pr. Ac. N. Sci. Phila., I, 1857, p. 84; Jl. 
Ac.cN. oct. Phila.,.JV;, 0858 4pe 53plevig tees uOhseavae 
LOSS) Pat 52s uple Vi cease. 
Margaren (Unio) jamesianus Les, Syn., 1870, p. 50. 
A widely distributed, very abundant and variable species. 
There are decided variations enough to make several perfectly 
valid species in the material [ have examined, but they are so 
completely blended together by connecting forms that 1t seems 
to me better to make varieties of them. The specimen figured 
by Say is much elongated, having the dorsal and ventral lines 
nearly straight and parallel. It is, according to the colored 
figure, yellowish-brown with an ashy tint and-has near the 
base, two narrow, concentric, tawny bands. lLea’s type of 
Unio jamesianus is a young and considerably distorted shell, 
being injured and drawn in at the middle of the base, and dis- 
eased along the hinge line, so that the hinge is curved upward. 
He has several fine, healthy shells which he calls jamesianus 
that agree with the type in texture, color and other characters, 
excepting form, and these are exactly like Say’s figure of 
tetralasmus. Generally it is smooth and shining, but I have 
seen specimens that are slightly dull. In Indian Territory, 
Southern Missouri and Texas specimens are abundant, which 
are often a little darker than the type, varying into dark brown. 
The dorsal and ventral lines of these specimens are sometimes 
a little curved and in Texas it runs into the variety manubius. 
Var. camptodon Say. 
Shell subrhomboid, the base line usually incurved when 
adult ; beaks sharper than in the type: surface dark, subshining 
or rougish ; nacre bluish-white. 
Length of Say’s figure 95, height 46, diam. 30 mm. 
States bordering the Gulf of Mexico. 
Type locality, New Orleans, La. 
