16 SCIENTIFIC SURVEY OF TURNER'S LAKE 
both the south and north ends. This condition may be better appre- 
ciated by comparing the results of investigations carried on in some 
well known inland lakes. Baker * found 91 species and varieties in 
Oneida lake, N. Y. and as many as 16 individuals per unit of 16 
square inches. Evermann and Goldsborough ° without giving particu- 
lar attention to the group collected 15 species in Chautauqua lake, 
New York. 
In the following species, the shells are all below normal size and 
unusually thin. 
Planorbis antrosus Conrad. This is a common species in the east- 
ern United States and Canada south to New Mexico. 
Physa heterostropha Say. Widely distributed in eastern states 
from Maine to Georgia, west to Michigan and Illinois. 
Musculium securis Prime. Common throughout the United 
States east of the Rocky Mountains. 
Pisidium abditum Hald. One of the most widely distributed mem- 
bers of the genus. Occurs in eastern Canada and United States 
south to South Carolina; also found in California and Honduras. 
CRUSTACEA 
ENTOMOSTRACA 
THe Water-FPLEAS 
(Identified by Dr. CHauUNcEY JupDAy, University of Wisconsin) 
The water-fleas are mostly minute forms which occur in great 
abundance in fresh water ponds, lakes and streams all over the world. 
In spite of their small size they are of great importance not only as 
the chief food of many young fishes but of certain larger species, 
like the white fish, that have specialized devices for straining them out 
of the water. 
In Turner’s lake eight species are found, all of which are well 
known and widely distributed. 
Collections were made by means of a conical net of fine silk drag- 
ged at the surface and at depths of fifteen and thirty feet. 
The species found at the surface: 
Diaphanosoma brachyurum (Liévan). ‘This species is common 
in marshes and in weedy margins of lakes and ponds. 
Ceriodaphia quadrangula (O. F. Muller). Common in all 
regions among weeds and in deeper waters of lakes. 
Bosmina obtusirostris Sars. This is a variable species found in 
pools and lakes in many regions. 
1. Tech. Pub. 9, N. Y. State College of Forestry, 1918, 18:181 
2. Rept. U. S. Fish Commission for 1901 (1902) p. 175 
