383 
to whose range are climatic, local, and ecological, but topographic 
only in a secondary sense. 
THE GENERAL DISTRIBUTION 
Most of the 150 species of the native fishes of Illinois range far 
and wide in all directions beyond its narrow boundaries, thus illus- 
trating the breadth and the simplicity of our geographical affiliations 
with the surrounding territory; but a considerable number, on the 
other hand, coming into Illinois from one direction, do not pass be- 
yond it in another, some part of the boundary of the general area of 
their distribution passing through our state. Several southern fishes 
go no farther north than Illinois; some northern fishes go no farther 
south; some eastern species find here their western limit; and a few 
western species range no farther east. The comparison of these geo- 
graphical groups whose areas overlap by their borders here in Illinois 
is a matter of special interest to the student of distribution, because 
it is in them that we find indicated the more remote affinities of our 
fish fauna, and from them, if anywhere, we may glean suggestions of 
its various origins. 
It will be convenient for a discussion of this subject to divide the 
general expanse over which Illinois fishes are distributed, into the 
following twelve districts: 1, the upper Mississippi Valley, including 
the Missouri and its tributaries; 2, the lower Mississippi Valley, in- 
cluding the Ohio and its tributaries ; 3, the far North, extending north- 
ward from the headwaters of the Mississippi, east to the Lake Supe- 
rior drainage, and west to the Rocky Mountains; 4, the far North- 
west, separated from the preceding by the Rocky Mountains range; 
5, the Great Lake region; 6, the district of Quebec and New England; 
7, the Hudson River district; 8, the north Atlantic drainage, from 
New England to the Chesapeake Bay; 9, the south Atlantic, from 
the Chesapeake Bay to Florida; 10, the peninsula of Florida; 11, the 
east Gulf district, bounded by the Mississippi drainage on the west; 
and 12, the west Gulf district, bounded by the Mississippi drainage 
on the east, and extending west and south to include the Rio Grande 
and its tributaries. The following table shows the recorded dis- 
tribution of our species over the territory so divided. 
