406 
district differs much less, eight of its one hundred and one fishes 
being without representation in our collections from the Illinois sys- 
tem. Next follows the Wabash basin in Illinois, with ninety-five 
species and a difference from the Illinois basin of 6.1 per cent.; the 
Galena district, with forty-four species and a difference of 4.6 per 
cent.; the Saline district, with fifty-five species, and a difference of 
3.8 per cent.;and the Mississippi and its marginal area, with ninety- 
seven species, 3.2 per cent. of which are wanting to the Illinois 
streams and lakes. The Kaskaskia and the Big Muddy, on the other 
hand, which are scarcely more than extensions of the Illinois district 
downward to the southern end of the state, contain virtually no fishes 
not in the main district, the Kaskaskia but one out of sixty-nine (1.4 
per cent.), and the Big Muddy none out of forty-two species. The 
Rock River district differs from the Illinois by only three species out 
of ninety-two (3.2 percent.). These data are presented more com- 
pactly in the table following. 
DIFFERENCES BETWEEN THE SMALLER DISTRICTS AND THE ILLINOIS BASIN 
; Species 
ae eee | foaad | ene 
Districts ae OT IEE of ae 
trict nois 
basin 
Distr OTS Re pea tt sy Sen ete rel ee eh LEU oe eR Ea oe 128 -_—— a 
AN Lol gt feces alps, ape Ral dient AG Lea cree es try CnC em re SE Si 9 6 
Cato May are he ee eects aL Ae ua eae Lo 101 8 08 
Wier balslia 0 ota cahtrs oes eeten eek ce Oise eee 95 6 .061 
(Gralla nyayeasi sn.» carte ire See Ree rie See ER | 2 046 
atiat GR ara own SNe ete ae Ie eG ee ee Ley Sey | 2 .038 
MASSISSITD Pie hteye the hoe eetrce ee Se core sae Sake SI amo tee 97 3 .032 
FO CLGARIVICT Meyer ie an ER tee Rec eet | 92 3 032 
HCAS leas claire vers cas See Pie, viens tees Uk Sach eee ies Cis s| 69 | 1 .014 
Sy Ta EM Glo bic Meee ate A toe Reel ia OL re er ee 42 0 .000 
