66 CORRELATION OF GEOLOGICAL FAUNAS. [bull. 210. 
graphical is not evident from the citation of these species alone. The 
presumption is that the strata at Milwaukee constitute an extension 
of the Hamilton formation of the lower peninsula of Michigan. The 
problem of determining the correlation of the fauna can be discussed 
more satisfactorily after the facts regarding the relations of the 
various faunas in the New York-Pennsylvania subprovince to one 
another are elaborated. 
HAMILTON FORMATION IN SOUTHERN ILLINOIS. 
In southern Illinois occurs a fauna, analyzed by Prof. Stuart Weller, a 
which contains three of the standard representatives of the Tropido- 
leptus fauna, viz: 
Chonetes coronatus. 
Phacops rana. 
Tropidoleptus. 
Some of the less common species of the New York Hamilton fornia- 
tion arc also reported in the list. 
The species enumerated constitute characteristic species of the 
Tropidoleptus carinatus fauna, and, although few, they seem to leave 
no doubt as to the presence of the fauna. But we are still left in 
doubt whether this faunule may not represent actually an earlier 
geological horizon than the base of the typical Hamilton formation in 
New York. 
The association of these species with species which do not appear 
in the typical Hamilton formation in New York confirms the opinion, 
derived from a comparison of the fauna with those outside the basin, 
that the Tropidoleptus fauna as a whole came into this interconti- 
nental basin from the south, and probably by a passage on the south 
side of the Ozark island of Missouri. If this hypothesis be correct, 
the association of the more typical species of the fauna with Onon- 
daga species in the southwest corner of the basin is not unexpected. 
The facts regarding the association of species in the faunules along 
the western side of the Cincinnati-Nashville axis, in Kentucky, Indi- 
ana, and Ohio, point the same way. 
SELLERSBURG FORMATION IN INDIANA. 
Recent investigation made by Dr. E. M. Kindle is revealing traces 
of the Tropidoleptus fauna to the west of the Cincinnati-Nashville 
ridge in central Indiana. 
In a report now preparing for the press, Dr. Kindle gives the fol- 
lowing list of species occurring in a Sellersburg faunule from a section 
in the town of Lexington, Scott County, a few miles north of 
Louisville, Ky. 
« Correlation of the Devonian faunas in southern Illinois: Jour. Geol., Vol. V, 1897, pp. 625 635- 
