530 General Notes. [July, 
some years the writer has been receiving specimens of a polymor- 
phous Anodonta, ranging geographically from New York to 
Western Iowa, including the important streams throughout this 
entire range. These shells have been received under the various 
specific names of Anodonta grandis Say ; A. plana Lea; A. decora 
Lea; A. hockingensis Moores, MSS.; and A. somersit Moores, 
very careful diagnosis of the exo-skeleton of all, and the 
soft parts of some of these, has convinced me of their specific 
identity. The following observations are based, in part, upon cor- 
respondence from various gentlemen who have kindly forwarded 
me specimens for examination. 
In Keokuk lake, about five miles from the city of Muscatine, 
Iowa, Anodonta grandis is found in great abundance. The shells 
vary in shape from a short full round form to a long and flat 
form; some are quite thick, others remarkably fragile for their 
size. For some unexplainable reason, as Prof. Witter writes, the 
young of grandis are rarely taken in this lake. Now, this re- 
markable diversity of form in this single locality is a fair repre- 
sentation of the increasingly proximate gradation in these above- 
mentioned species from New York to Western Iowa. The form 
known as decora Lea, from New York could not be distinguished 
readily from the grandis at Muscatine. The shells from that 
State are less heavy than from any other section represented in 
my cabinet. The Eastern forms are more compressed as to the 
beaks, rather more inflated, and having the posterior dorsal slope 
rather more oblique. From Ohio were received forms with much 
thicker shells, and white prismatic nacre. Both decora and plana 
from that State has a much more brilliantly colored epidermis 
than any of the more Western forms. In this respect they sustain 
to grandis essentially the same relation that the brilliantly colored 
Unio siliquoideus, sustains to U. luteolus Laur., of which it is only 
a variety. In Indiana, Illinois, and Iowa, the most marked differ- 
ence appear to be in the coloration of the nacre, which varies 
from white to a very deep salmon, the latter being the most con- 
stant color in the Western limit. The two species described by 
Mr. Moores, mentioned above as manuscript descriptions, are, be- 
yond doubt, the young of grandis. Carefully comparing all my 
specimens, some sixty in all, with typical grandis, the conclusion 
reached was that these forms are all varieties of Mr. Say’s shell, 
the mantie, some of them being sexual 
