256 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
It will be noted that in this section there is a formation added at 
the top which is even younger than any found in New York and that 
it is characterized by a fauna differing in a considerable number of 
species from the fauna found below. The strata containing this 
fauna are at the base, limestone, but above pass over into dark shale 
which becomes finally typically “Utica” in facies. The transition 
from the limestone of the Picton into the limestone of the Collingwood 
is gradual and some of the species of the Picton continue into the 
Collingwood; there is probably no break in sedimentation. 
MINNESOTA. 
These formations, or at least most of them, can be traced across 
Ontario to the westward and in Minnesota the following section may 
be seen (Winchell and Ulrich, 121). 
Feet. 
8. Massive dolomitic limestone with Maclurites and Mac- 
lurina. Stewartville dolomite. 50 
7. Fine grained to subcrystalline limestone with some 
argillaceous layers in the upper portion. Among the 
fossils are Rafinesquina deltoidea, Zygospira uphami, 
Fusispira nobilis, Fusispira inflata, Cyclospira bisulcata, 
etc. 56 
6. Cherty limestone with Orthis tricenaria, Clitambonites 
_ americanus, Parastrophia hemiplicata, ete. Clitambon- 
ites bed. 9 
5. Mostly thin-bedded limestone, argillaceous in the lower 
portion and becoming more pure toward the top. 36 
Zones 7 to 5 belong to the Prosser limestone. | 
4. Blueshales with branching sponges. Fucoid bed. 6 
3. Blue shales with Bryozoa and Ostracoda. Phylloporina 
beds. 14 
2. Shales with limonite, sometimes odlitic in structure. 
Many Pelecypoda. Ctenodonta bed. 9 
1. Dark green soft shale with numerous Bryozoa. Rhini- 
dictya bed. 23 
Zones 4 to 1 make up the Decorah shale. 
There are two subdivisions of the Trenton strata in Minnesota 
which may be correlated directly with formations in Ontario. These 
are the upper strata of the Prosser limestone, (zone 7 of the section 
