Faunal Provinces of America. — Schuchert. 147 
Thedford Hamilton fauna is listed by Shimer and Grabau* 
and is compared with that of Eighteen Mile Creek, to the west 
of Buffalo, New York. The Thedford fauna has 236 named 
species and of these 87 also occur near Buffalo, but 129 in 
the entire state of New York. If we add the 12 other species 
known in this state only in the Onondaga, it follows that 141 
New York Middle Devonic species are common to the two 
places, or that 61 per cent of the Thedford fauna also occurs 
in New York. Not only is the percentage of species common 
to the two places high, but the forms are also those most 
characteristic of the New York Hamilton. 
In a straight line it is 330 miles from Thedford west to 
Milwaukee and 180 miles from the first named place north to 
Alpena on Thunder Bay. Michigan. The latter region still 
has. many of the characteristic Thedford Hamilton forms, but, 
as stated elsewhere, has also a considerable number of west- 
ern species. This mixed fauna — Traverse — therefore occurs 
between Thunder Bay on the east side of Michigan, and Mil- 
waukee on the west side of Lake Michigan. 
It seems to the writer that the facts just mentioned demon- 
strate that there is a very marked difference in the Middle 
Devonic faunas of Missouri and Iowa when contrasted with 
those of Thedford, Ontario, southern Illinois and the Louis- 
ville, Kentucky, region. The former places belong in the Da- 
kota seat and the latter in the Mississippian sea.ii: This is 
also the conclusion of Calvin and he writes in T898 as follows : 
"The Devonian system of Iowa was deposited in an area 
geologically isolated from that in which the eastern Devonian 
was developed. The conditions of sedimentation were differ- 
ent in the two areas. The order and succession of faunal con- 
ditions were not the same. The eastern Devonian faunas, sub- 
jected to certain physical conditions and undergoing certain 
* Bull. Geol. Soc. Amer., xiii, 1902, pp. 149-186. 
f Williams names this sea the Dakota channel but it is more properly re- 
garded a sea, not only because of its great length, but of its great width as 
well. It is defined us follows: 
"From the north a wide open oceanic channel swept from the Mackenzie 
river valley region across British America, the Dakotas, Nebraska, and Kansas 
[also Iowa, south-eastern Minnesota, Missouri, northern Illinois and south- 
eastern Wisconsin] far into and through the western Texas region to thesouth. 
This channel was bounded on the west by the extensive A rchean islands or 
edges of land constituting: the eastern axis of the present Kockv mountains." 
Amer. Jour. Scl., May, 1897. p. 394-. 
% For definition of Mississippian sea see Walcott, Amer. Assoc. Adv. Sci., 
1894, pp. 129-169. Ulkich and Schuchert, Bull. 52, N. Y. State Mus., 1902, 
p. 636. 
