150 THE CHICAGO ACADEMY OF SCIENCES. 
all have been subjected to some peculiarly unfavorable influence. he 
specimens from Black Lake are a pure translucent white. If the forms 
figured on the plate referred to (pl. XXH, figs. 1, 2) were constant 
they would constitute a marked variety of stagnalis. Mr. Walker says 
of these, in a recent letter, that they vary toward the normal form and 
that in his opinion they are not entitled to be given varietal rank. 
He also says: “The set I have varies greatly in shape and several 
of them are deformed. Another has the edge of the lip completely 
revolute. Figs. 2 and 3 are the most regular.” In the Smithsonian 
Institution there are three specimens similar to those figured by Mr. 
Walker. These measure as follows: 
Aperture 
Length. Breadth. length. Breadth. 
33.00 16.50 22.00 10.25 mill. Lake Erie 
22.00 14.25 19.25 8.00 ‘“ Ruby Valley. 
29.00 15.00 18.50 9.00 as 
The Lake Erie specimen (No. 41716) was collected by Dr. Dall 
and the Ruby Valley specimens (No. 27953) by Capt. Simpson. This 
form is similar to var. acuminata Lam., clammys Bens., and succinea 
Desh., which are peculiar to India. 
In the Niagara River at Squaw Island, near Buffalo, N. Y., occurs 
a form of appressa with a much expanded aperture, recalling some 
of the mutations named by European conchologists. Some specimens 
have the upper part of the aperture much flattened. It is upon just 
such material as this that some of the French conchologists have made 
two score or more species and varieties of Lymnea stagnalis. The 
shell of stagnalis is frequently distorted, the whorls becoming scalari- 
form and developing a marked shoulder. Such specimens have been 
seen from Spoonbill Slough, Deuel County, South Dakota. 
Lymnea stagnalis var. Plate XXII, figure 4. 
Limnea stagnalis var. bottnica? WaA.kKerR, Nautilus, IX, p. 3, 1895. 
“Among the fresh-water pulmonates many interesting forms oc- 
curred. The most noteworthy of them was a single example of a 
deep-water form of Limnza stagnalis L., dredged from ten meters 
depth in Lake Michigan, at High Island Harbor, in the Beaver Island. 
It is about 23 mm. in length, exceedingly fragile, of a pure translucent 
white, and, though somewhat larger and differently proportioned, ap- 
pears to be analagous to the var. bottnica of Clessin from Sweden.” 
(Walker, Nautilus, p. 3.) 
This is a peculiar shell and additional material may prove it to 
represent a recognizable race of stagnalis. Mr. Walker says of it: 
“The white form of L. stagnalis mentioned in Nautilus IX, p. 3, was 
