150 WEST AMERICAN SHELLS 
cludes L. umbrosa, Say, and probably several 
other forms. This animal lives along the north- 
ern tier of States, from New York to the Pacific. 
It is also found in the Sacramento and Columbia 
Rivers. 
Limnea kirtlandiana, “ea, Kirtland’s 
Limna, is shown in Figure 130. The shell 
is dextral and somewhat eylindrieal, the 
spire long and five-whorled, the aperture 
rather small and oval, and the columella is 
marked with a fold. The cut is somewhat 
magnified, as the natural size is from one- 
half to three-fourths of an inch. 
A common shell that is found in many of the 
brooks and streams over much of the Pa- 
cific Coast, as well as east of the Rocky 
Mountains, is shown in Figure 131. Its 
name is Physa heterostropha, Say, the 
Reversed Physa. The shell is thin and 
delicate, of a hght horn-color, with a 
small spire, a sinistral aperture, and is commonly 
about half an inch in length. The animal is black 
or nearly so, and when the shell is inhabited it ap- 
pears much darker than when it is empty. 
It is amusing as well as instructive to put some 
of these little creatures in a jar of water and watch 
their movements. Sometimes they will quietly re- 
main at the bottom, eating the pulp of an alder 
leaf that you have given them; then they will rise 
to the surface to take a breath of fresh air and 
slowly sink back again, or perhaps they will erawl 
along, shell downward, apparently clinging with 
