330 THE CHICAGO ACADEMY OF SCIENCES. 
from the left very large and roundly triangular, the side cusps, 
two onthe left and four on the right, sharply triangular; lateral 
teeth long and narrow, the lower ends rounded, the reflections 
very wide and low, the first twelve-cuspid and the second six- 
teen-cuspid (Fig. 117). 
Distribution: Europe and America (the latter introduced), 
New York, Ohio, Illinois, Michigan, Wisconsin. 
Geological distribution: Pleistocene. 
Habitat: Inthe larger lakes, onasandy or muddy bottom, 
and attached to sticks, stones, and other submerged objects. 
Remarks: This is the largest species of Ammnicolide found 
in this region. It may be easily distinguished by the size of 
the last whorl, which more than equals in length that of all 
the rest. The species was introduced into this country many 
years ago and is now found from Vermont and New York to 
Wisconsin. It is particularly abundant in Lake Michigan. 
While in motion the animal of Bytiinia is rather slow, the ten- 
tacles move about nervously and the rostrum is thrust out to 
its fullest extent, Thus far it has been collected only in Lake 
Michigan. 
Recently the Lake View water supply has been seriously 
threatened by the presence of this snail. The small service 
pipes became choked and in many private houses a tumbler- 
ful of these animals was taken from the faucet. Investigation 
at the Lake View crib showed that the screens were provided 
with such a large mesh that the eggs gained access to the main 
tunnel and there developed, the force of the water drawing 
them farther and farther into the tunnel until they finally ap- 
peared in the service pipes. Besides this species, Pleurocera 
elevatum and Goniobasis livescens were found about the crib, 
but none on theinside. These were collected in August, 1898. 
Subfamily Hydrobiine. 
Shell: Small, elongated or globose, umbilicated or rimate; 
aperture rounded or ovate; peristome continuous; operculum 
paucispiral, corneous (Tryon), without internal process. Foot 
without lateral sinuses. (Stimpson.) 
Genus AMNICOLA Gould and Haldeman. 
Shell: Small, thin, smooth, globose, umbilicated; spire 
broadly conic; aperture broadly ovate; outer lip thin; opercu- 
lum subspiral, corneous. 
