150 The American Geologist. September, 1903 
sea invaded the area of these states and spread northward 
through Traverse straits (taking its name from Traverse- 
formation) along the western side of the Kankakee peninsula 
into northern Michigan where it came into more or less un- 
restricted communication with the Mississippian sea. The 
general trend of the Kankakee axis is northeast from southern 
Illinois to the region of the Kankakee river where it seems to 
be flexed, following the general trend of that stream and again 
bending, strikes northerly through the western part of the 
Lower Peninsula of Michigan. The change of strike along the 
Kankakee river seems to be due to another axis having a 
northwest-southeast direction and named by Gorby* the Wa- 
bash axis. The name for the heretofore unnamed axis has 
been taken from the Kankakee valley since it is to the west,, 
south and east of this region that the lay of the Devonic de- 
posits against the Niagaran and Cayugan formations can be- 
observed in outcrops or by means of well records. In the south 
the Ohio and Mississippi rivers have eroded through the uplift 
where rocks of Middle and Upper Devonic age of the Missis- 
sippian type are at the surface. Not only this, but in Hardin 
county, Illinois, Worthen and Englemannf describe a low arch, 
near Elizabeth. Otherwise the greater portion of the original 
uplift now lies buried beneath the "Eastern Interior Coal 
Field" and the "Northern Interior Coal Field." 
The writer has now pointed out some of the faunal features 
that distinguish the Dakota and Mississippian seas during the 
Middle Devonic. The area of these seas, the Cincinnati island, 
Kankakee peninsula, and the margin of the bordering lands are- 
in a general way shown on the accompanying maps. It has 
also been shown that the Dakota and Mississippian seas inter- 
mingled to some extent while the intermigration of species is 
believed to have been most decided during the Upper Devonic. 
The migrants appear to have traveled from Iowa into Xew 
York along the southern shore of Laurentia. This is the gen- 
erally accepted view and it has much to recommend its accept- 
ance, but that the decidedly European fades of the Naples 
fauna in the Upper Devonic of New York also came along the 
same shore as stated by Clarke, the writer cannot believe. 
•Fifteenth Rep. Geol. Surv. Indiana, 1886, p. 228. Orton, Eighteenth 
Ann. Rep U.S. dcol. Surv., 1889, p. 5S0; Kindle, Amer. Jour. Sci., June,. 
1903, pp. 461. 463 
t Geol. Surv 111., i. 1866. p. 352. 
t -V. Y. State Museum, Rep. State Pal., 1902, p. 670. 
