EHARLY SILURIAN ROCKS IN HUDSON BAY REGION 330 
In Michigan the strata containing Camarotoechia ? wintskensis, 
Isochilina grandis var. latimarginata, and Leperditia hisingert var. 
fabulina conformably overlie the Virgzana mayvillensis beds, and 
thus are thought to correspond in age to about that of the Sexton 
Creek or Kankakee limestone which overlies the Edgewood in 
Illinois and Missouri, but they were deposited in a different geologic 
province. 
The close correspondence in the fauna of the strata overlying 
the Virgiana mayvillensis zone in northern Michigan with that of 
the strata above the horizon of Virgiana decussata in the Hudson 
Bay and Saskatchewan regions leaves no doubt of the equivalence 
of the strata containing this fauna in the areas above mentioned. 
They also prove that the Vzrgiana mayvillensis zone in Wisconsin 
and Michigan, and the Vzrgzana decussata zone in the Hudson Bay 
and Saskatchewan localities represent the same stratigraphic 
horizon. 
Besides the above-mentioned localities Hume’ has found early 
Silurian strata containing Camarotoechia? winiskensis, and numer- 
ous ostracods in the Lake Timiskaming area that he correlates with 
the Cataract formation, which doubtless corresponds with the 
Camarotoechia? winiskensis, Isochilina, and Leperditia horizon in 
the.regions above described. The age assigned to this horizon by 
Hume agrees with that given by the writer above. 
Kindle? found Silurian strata several hundred miles north of the 
Grand Rapids locality, in the vicinity of the Pas, from which he 
obtained the fossils Camarotoechia? winiskensis, Pterinea ct. 
occidentalis, and Leperditia cf. hisingert. This fauna also indicates 
a horizon about equivalent to that of the Silurian in the Lake 
Timiskaming region and to the strata containing Pterinea occiden- 
talis, Isochilina, and Leperditia, above the Virgiana decussata 
horizon in the Grand Rapids section, the latter horizon not being 
exposed in the more northern locality. From the similarity in the 
faunas of the Virgiana zone, and of the higher strata containing 
G.S. Hume, ‘“ Paleozoic Rocks of Lake Timiskaming Area, Geol. Surv. of Canada, 
Sum. Rept. (1916), pp. 188-92. Fossils reported by Charles Schuchert in a personal 
letter. 
2. M. Kindle, op: cit., p. 12. 
