GENERAL AND INTERIOR DISTRIBUTION Ixix 



other hand, coming into Ilhnois 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. 



