266 THE AMERICAN MIDLAND NATURALIST 
flat on the center of the disc, it may not be the typical dakota of 
Frierson. In other respects the shell structures are identical 
with those of A. grandis. 
Sex Length Width Diameter Locality 
OSTA Xe Seka aS (L. Contrary, St. Joseph, Mo.) 
SOS) o Xieu7 3 Xe One (L. ee “a dd nee a) 
MISCELLANEOUS REMARKS:—This truncated form may only 
be the result of a local reaction on grandis as it is not often found 
in very quiet water but in the more disturbed water near the 
shore, yet its occurrence in such a constant shell-form is so common 
in our Missouri lakes that it would be safe to assign it to the defi- 
nite species herein referred, or at least its subspecies. Dr. Ortmann 
thinks this form may bear the same relation to our western lakes 
as A. benedictis (a form of grandis-footiana) does to Lake Erie 
where it is grown close to the shore in the surf. 
Anodonta corpulenta Cooper. 
(“Big Floater,” ‘Slop Bucket.’’) 
Not figured. 
1834—Anodonta corpulenta Cooper, App. to Narrative, Exp. Miss. R. 
to St. L., p. 154.—B. W. Wright Check List, 1888. 
ANIMAL CHARACTERS :—The nutritive and reproductive struct- 
ures are identical with those of A. grandis; however, its glochi- 
dium is different in shape and size, having an irregular, undulate, 
hinge line with length and depth equal (0.350 x 0.350mm.). 
SHELL CHARACTERS:—With the exception of a shorter, 
wider, more inflated shell and also of more recurved beaks the 
shell is the same as that of A. grandis. 
MISCELLANEOUS REMARKS:—Some students of Nazades are 
inclined to call corpulenta an “overgrown grandis.’’ However, its 
smaller, but most of all, its differently formed glochidium would 
separate it from grandis since nothing is so constant as glochidial 
characters. This form is reported as rather common in the sloughs 
and lakes along the Mississippi in this state; yet it is not found 
in the lakes of North-west Missouri. Simpson reports it for the 
Missouri river (1900b, p. 646) but is not specific about the locality 
and states that it has a general distribution for the upper Mississ- 
ippi River east to Indiana and south to Texas where it may be 
replaced by A. stewartiana. Dr. Surber (1913, p. 106, Pl. XXIX, 
fig. 1) has found this species to be an occasional fin-parasite upon 
ae 
