PAPERS ON ZOOLOGY 151 
Among stream fishes, the distribution of species and variants 
is usually correlated, not with latitude or area, as in the case 
of terrestrial animals, but rather with the extent of the stream 
basins themselves: for the history of the streams and the his- 
tory of the stream fishes are intimately connected. The case of 
the golden shiner forms one of the apparent exceptions to this 
general law, for in Notemigonus the distribution of the vari- 
ants seems to be correlated with area and perhaps with temper- 
ature, rather than with the stream basins. A closely similar 
case appears to occur among the sun-fishes, and others will 
probably be demonstrated when our freshwater fishes are 
more extensively studied. 
THE MOLLUSCA OF PIATT, CHAMPAIGN, AND 
VERMILION COUNTIES OF ILLINOIS 
JAMES ZHTeK, Board or HeauttH LaBsoraTory, ANCON HOSPITAL, 
ANCON, CANAL ZONE 
This report on the mollusks of these three counties is based 
upon collections and observations made from the Autumn of 
1907 to the Summer of 1911, supplemented by such additional 
data as given in Baker (1906). The late Mr. Charles A. Hart 
accompanied me on a great many of these excursions and took 
a lively interest in the study; to him particularly I wish to 
show my gratitude. 
I am also greatly indebted to the following gentlemen: Dr. 
Charles C. Adams for valuable suggestions and interest in the 
survey; to Dr. Frank C. Baker for accurate determinations of 
my material and checking on my identifications; Dr. Victor 
Sterki for identifications of the Spheriide and Ppide; Dr. 
Bryant Walker for determination of Paravitrea significans; 
my colleagues, Drs. J. Douglas Hood, Arthur G. Vestal, Robt. 
_D. and Hugh Glasgow, H. E. Ewing and Frank Elmer Wood, 
for contributions of specimens; Drs. Wm. Healey Dall and 
Paul Bartsch for their kindness in going over the manuscript 
and bringing the nomenclature to date; and finally to the 
pioneer ecologist, Dr. Stephen Alfred Forbes, for the use of his 
library and for valuable suggestions. 
