416 THE CHICAGO ACADEMY OF SCIENCES. 
from Maine, Michigan, Wisconsin and Minnesota has demonstrated 
that the species is divisible into a number of fairly well-marked races. 
In all of these races there are some individuals which approach typical 
emarginata in general form showing that all have sprung from the 
same stock. Each race, however, expresses a certain facies which 
easily separates it from the typical form and from the other races. The 
-elationship of these races may be expressed as follows: 
emarginata 
wisconsinensis 
mighelsi 
angulata 
ontariensis 
canadensis 
Wisconsinensis is somewhat related to mighelsi and angulata, but 
on the whole seems to present characters which place it as an inde- 
pendent branch of emarginata. 
The Maine emarginata varies toward mighelsi, some individuals 
being of such a transition character that they cannot be definitely 
placed in either form (as figures 10-11 on plate XLIII). As a rule, 
however, the rounded aperture and more elevated spire will separate 
the two forms. The figures on plate XLIII well illustrate this varia- 
tion. Emarginata from Michigan and New York are more uniform 
and less difficult to determine. Specimens from Western Ontario 
(especially Rainy Lake) vary towards mighelst. 
Galba emarginata mighelsi (W. G. Binney). Plate XLIII, 
figures 13-21; plate XLI, figure 25. 
Limnea ampla MicHeEts, Bost. Journ. Nat. Hist., 1V, p. 337, 1843; Bost. 
Journ. Nat. Hist., IV, p. 347, pl. 16, fig. 1 a to 1c, April, 1843 (not of Hartmann 
1842) ; Proc. Bost. Soc. N. H., 1, p. 129, 1843.—Stimpson, Sh. N. Eng., p. 52, 1851. 
—WuitEAVEs, Can. Nat. & Geol., VIII, pp. 102, 112, fig. 11, 1863—Brnney, Check 
List, p. 12, 1860; Land & F. W. Sh. N. A., II, p. 30, fig. 34, 1865—Morse, Amer. 
