Dec., 1912.] Ordovician Section, Lake Huron Area. 
43 
but no good exposures have been found. Te.tradium bundles 
occur at 45 feet above the lake, and massive specimens are found 
4 feet farther up. 
The strata immediately above the Tetradium horizon consist 
of fissile black shales interbedded with limestone near the base. 
These strata were formerly regarded as Utica, but they probably 
represent an older formation than the Utica of New York, and 
recently Prof. Percy E. Raymond has proposed for them the name 
Collingwood. Their most characteristic fossil is the trilobite 
long known as Asaphus canadensis. Triarthrus spinosus, and a 
graptolite, identified by Dr. Ruedemann as Diplograptus quadri- 
mucronatus , also occur. At Little Current, 11 feet of this Colling¬ 
wood shale are exposed, but the total thickness may equal 20 feet. 
7. Cincinnatian Beds on Manitoulin. 
A. Sheguindah Beds; Eden. 
Along the road from Little Current to Sheguindah, the strata 
immediately overlying the Collingwood formation are exposed at 
several localities. One of these extends from three miles southeast 
of Little Current southwards up the hill. Here the top of the 
Collingwood is overlaid by shales which near the base are blackish 
but much softer. Within 9 feet of the base, these clay shales 
contain a species of Triarthrus. A small Primitia and a Leptobo- 
lus extend from the base upward for about 37 feet. The only 
species of graptolite noted is fairly common, and was determined 
by Dr. Ruedemann as nearest to Diplograptus peosta, but with 
closer arranged thecas; it ranges from the base for 43 feet upward. 
Dalmanella appears at 25, between 37 and 43 feet, and at higher 
levels. The first trace of limestone was found 43 feet above the 
base, but limestone layers do not become common until an eleva¬ 
tion 100 feet above the base has been reached. 
It is in these upper limestones and in the interbedded clays 
that the typical Eden fauna listed below occurs. The fossils 
were examined by Ulrich, Bassler, and Nickles conjointly, the 
determinations being only provisional, until microscopic slides 
can be prepared. Along the Sheguindah road, Amplexopora 
persimilis, Callopora sigillarioides, Coeloclema communis , Hemi- 
phragma whitfieldi, Perenopora vera, and a Stigmatella near clavis 
or nana occur. From the corresponding strata at Tamarac Point, 
10 miles southwest of Little Current, Aspidopora cf. areolata, 
Arthropora clevelandi, Bythopora arctipora, and Primitia centralis 
occur in addition to those already named. At the corresponding 
horizon at Gorrel Point, two miles northeast of Gore Bay, Aspido¬ 
pora eccentrica, Bollia persulcata , Bythocypris cylindrica, Jonesella 
crepidiformis, Primitia cincinnatiensis , and Acidaspis crossotus 
are added to the list. At the exposures immediately south of 
the high Richmond Clay Cliffs, on the eastern side of Cape Smyth,. 
