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INTERIOR DISTRIBUTION. 
Table of Interior Distribution—by River Systems. Species and Num- 
DemROMme OllectOnStOlsey AChie Ameren Rainateh une es ery cha che eis Sie beee 8 pO 
The lllinois Basin and the other Districts compared.................. 401 
Species of the Illinois Basin and Number of Collections of each........402 
[itnois Species not found in the Illmois Basin... -.....5..0....54.. 405 
Differences between the Smaller Districts and the Illinois Basin...... 406 
Lists of Species distinguishing different Districts from the Illinois 
[By SISTER ¢ | SERBS seth ita Late veiehah Goln SRc ENON SHE Ee MLR NC eto y acon to al thot Re cee eRe ea iene ogee 408 
Relanonsroleachs Distrctitorallethnerothersha. = qa. soc o7es seine ee - 408 
Number of Species Common to each Pair of Districts, and Ratios to 
PHEW GmMHer Ol mpecies ah CAChMP Att 6.5 occ HS ke wig nk ale tena lb ele 409 
The Fishes of Northern, Central, and Southern Illinois............... A414 
Mishessotliumibed Distrib ubioneiny UllimMOiS wares: eeetns soo Jee aoe 412 
WiseroleWocaltisy aici skis aati sree: 6 eager Ss Menu eager, sien aie chavat specs alle g 415 
Pecularities of Distribution in the Lower [llinoisan Glaciation........ 416 
Fishes Rare or Wanting in the Lower Illinoisan Ge eeion bola ee 417 
Fishes Tolerant of the Lower Illinoisan Glaciation. eee ERe Acheron M ae at 
Glacscsiicaponmandawse om colocical sD atan1...2)..4 ace seeds aioe 419 
Fishes of the Ohio and of the Mississippi Drainage.....:............- 420 
Disibuttonvehiehweine tae! OhjiosDrainagtet =. 442 ie ae ae 421 
Distribution chiefly in the Misssissippi Drainage................... 421 
jhoundary between Northernvand Southern Species... 0... tee 422 
Generalpheatures of ecological Distribution: >.\. oa. 5.....---..+555 65 422 
eo loedCaledualn le mpeg wir are aun crane AED en tse ce riya edo sicker d,. pt Pegaveus ee 427 
(Gievaueiraill Sygate nen nea ake crore ote Soe ALOE Bec Ole ee OORT OC ee ee ner POR eR ee ec nade 432 
IL FISI8 Gil IMIENOSS eke 6 a rhea ode cetera tear San sea me 436 
ARTICLE IV. THE ECOLOGY OF THE SKOKIE MARSH AREA, 
WITH SPECIAL REFERENCE TO THE MOLLUSCA. BY 
FRANK COLLINS BAKER. (20 Prates; 4 TExT FIGURES, INCLU- 
DUNC MVEA) eeU ME RIAU Ve HOO) ae bs. porate vy kesee, Soc op) shit eis ecesl Jac ei has 441-499 
ICPRGDU COIN ae Shae ts ce Sree ca eae ne eae ee ek are 441 
IWilertlaveyal Lt SiRGVG i733 en oho careec oe Aen onan eR ee eran oe RR ec 441 
Je leat onALSGNEREOOVESENES are Sadat ate aoc get leren oko Snares pCR pennant ae 442 
Heomomncr@OnsiG eratlOUSem nr. cei or 427.2 acute isragen ata vhs Meets eee | 442 
(Generalelo poonap li ~ewenyen eae ros hai .s See gee bose thine ayo 3 443 
JAS « MUGS. 'SUe3) 6 teh ai gol abe eae geen a ne ee 446 
B. The Intermediate Ridge or Sand Spit.. =e PAS milo 
C. The East Branch of the North Branch a ihe Chicsee er Secs 447 
er ihe re lenwmoud Beach) hag ee. Pe. 22 ft naee ew aati ey oats elle 447 
Bee bnew Nor nebiranchiom Gre: Gbicaso nvete ser lr. sy-0 (ler eyeners 2156 448 
RESO lu Mo MiP ATISONS Sach one weet oa ingen uh tenn MN A te hain aie, 41g SS 449 
DetatedsDiscussion/and Comparison Of statiGnhs. . i. in- e es ete ele 0 449 
AES Kokien\iarshmotanons lang: [lie artan ass mec ack a ociok ins se aes 449 
Baeuevincermediace Ridge: Stationsylll' to XOX. ne 5 452 
