THE NATURAL HISTORY SURVEY. 55 
or salmon colored. In some specimens the hinge line and edge 
of valve are mauve while the interior is salmon colored. 
Length, 100.00; height, 63.00; breadth, 55,00 mill. J (7165). 
us OSOOR sas bbe: ns AACO0 at 3 ($299). 
ss S1O02 > ets 48.00; ot 31.50 ‘' © (1698). 
os 51.00; ae 32.00; L 21 b0" — (9844) Juvenile. 
Animal: Not differing essentially from Anodonta grandis. 
Distribution: Northern part of the United States and Can- 
ada. A species of the St. Lawrence drainage, but sometimes 
found in the Mississippi drainage. 
Geological distribution: Pleistocene. 
ffabitat: Similar to that of 4. grandis. 
Remarks: The present species is very closely related to 
A. grandis and would, perhaps, be more correctly placed as a 
variety of that species. I am much opposed to the idea of vari- 
eties in this family, from the fact that it is difficult to find con- 
stant characters within the species. It seems to me that when 
tangible characters are present the form should rank as a spe- 
cies. The specimens before me show the following distinctive 
characters: In /footiana the umbonal region is very much in- 
flated and the anterior and posterior angles are very sharp; in 
grandis the umbonal region is more flattened and the angles are 
more gentle; in /footzana the umbones have four fine, distinct 
wrinkles while in grandis there are five coarse ones; /ootiana is 
generally light green or brownish horn in color, while grands is 
generally dark green or black. /votiana belongs to the St. Law- 
rence drainage, while grandis belongs to the Mississippi drain- 
age. The two species frequently overlap, however, and there are 
many forms which are difficult to place. Gyvandis is by far the 
most common of the two species in this region. The specimens 
from Berry Lake (No. 7165) are unusually corpulent, those 
found at Winnetka (Nos. 9298-9299) being more typical. 
GROUP OF ANODONTA IMBECILIS. 
Shell rather thin, smooth, shining; umbonal region usually 
flattened, often rayed with delicately waved fine lines. (Simp- 
son.) 
3- Anodonta imbecilis Say, pl. v., fig. 1. 
Anodonta imbecilis Say, New Harm. Diss., Vol. II., No. 23, p. 355, 1829. 
Anodonta incerta Lea, Trans. Amer. Phil. Soc., Vol. V., p. 45, pl. vi., 
fig. 16, 1832. 
Anodonta hordea Gou pn, Proc. Bost. Soc., N. H. Vol. V., p. 229; 1855. 
