54 THE CHICAGO ACADEMY OF SCIENCES. 
A large number of specimens were dissected to ascertain if 
any tangible differences could be found in the shell between the 
sexes, but with a decided negative result. No differences could 
be found, excepting that the females were generally larger. A 
male and female of equal size gave the following measurements: 
Length, 108.00; height, 67.00; width, 50.00 mill. J 
“408.00; 65.00; ‘ 48.00 “ Q 
In all the females the outer branchium only was used as a 
marsupium and this was of a dark brown color, very much 
swollen and so heavy that the least touch caused it to rupture. 
The glochidia were fully developed and very active, and seemed 
ready to be discharged into the water. 
2. Anodonta footiana Lea, pl. iii., figs. 2, 3, 4; pl. iv., fig. 2; pl. viii., 
fig. 5. 
Anodonta footiana Lea, Trans. Amer. Phil. Soc., 2d series, Vol. VIII., p. 
225, pl. xx., fig. 44, 1843. 
Anodonta marryattana LEA, |. c., Vol. VIII., p. 226, pl. xx., fig. 45, 1843. 
Anodonta opalina ANTHONY, Amer. Journ. of Conch., Vol. I., p. 159, pl. 
xiv., fig. 2, 1865. 
Anodonta subangulata ANTHONY, Amer. Journ. of Conch., Vol. I., p. 158, 
pl. xiii, fig. 1, 1865. 
Anodonta McNeilit ANTHONY, Amer. Journ. of Conch., Vol. II., p. 144, pl. 
vi., fig, 1, 1866. 
Shell; Thinner than A. grandis, much inflated, suboblong 
rounded before and triangular behind, the apex of the triangle 
truncated; dorsal margin straight; ventral margin straight or 
slightly rounded; posterior margin elliptical in the male and 
plough shaped in the female; surface marked with growth lines 
as in grandis; umbones not much elevated, light yellowish green 
in color, but generally eroded and pearly, and marked by four 
distinct, elevated, wavy wrinkles, arranged as in grandis, but 
very much finer; sometimes there isa fifth, very faint ridge; 
ligament strong, dark horn color; epidermis generally light 
greenish straw colored, varying to straw colored, horn or reddish, 
and generally without rays of any kind (sometimes very faintly 
rayed); umbonal slope very much rounded, owing to the greatly 
inflated umbonal region; hinge line very slightly curved, a trifle 
thickened; adductor muscle scars, protractor pedis muscle scar 
and pallial line distinct but not impressed; dorsal muscle scars 
as in grandis, small, slightly impressed; cavity of the beaks deep, 
inflated; nacre silvery white, iridescent, sometimes light mauve 
