[amr] SYNOPSIS OF THE GEOLOGY OF CANADA 205 
from the Arctic regions have been described by Dr. Etheridge, Mr. 
Salter, and other writers, and indicate a Niagara or Wenlock age. 
In the Lake Temiscaming basin Silurian fossils abound and are well 
preserved, some eighly species having been recently collected by Dr. Bell 
and Dr. Barlow, and these have since been studied and determined by 
Mr. Lambe and the writer. The horizon of this outlier was determined 
by Mr. Billings from fossils obtained by Mr. James Richardson, one of 
the staff under Sir William Logan in the early years of the Geological 
Survey of Canada. 
The Lawrencian Lowlands.—Thin bedded limestones and shales in 
Anticosti form an important area of Silurian rocks. To this peculiar 
development Mr. Billings gave the name of Middle Silurian, inasmuch 
‘as the limestones of the Lorraine or uppermost Ordovician formation of 
this island passed upward without any break in lithological character 
or origin of sedimentation into several divisions or life zones which find 
their equivalent in other parts of Canada, in the Medina, Clinton, and 
Niagara formations. Local designations for the various members of the 
Silurian strata of Anticosti, based upon the faunistic relations which 
exist between the divisions as separated by Billings, will, it is hoped, 
shortly be discussed by the writer. 
Isolated areas in the province of Quebec, referable to the lowest 
division of the system, namely, the Medina, occur on the south shore 
of the St. Lawrence, along the Yamaska river south of Lake St. Peter 
and notably near St. Grégoire, Que., where a strong brine has recently 
been struck. The Medina formation at this point is probably not less 
than 600 feet in thickness. On St. Helen’s island, opposite Montreal, 
and on Belceil mountain (Montagne de Belceil), the Lower Helderberg 
formation which has been held for such a long time to represent the 
summit of the Silurian system in North America, may be seen in some- 
what limited patches of compact and considerably altered light-gray 
limestone which abound in fossils. There is little doubt that at one time 
the Silurian system extended widely throughout the St. Lawrence valley, 
but Post Devonian erosion has carried off nearly every trace of its ex- 
istence. 
In Ontario, the Silurian system is well developed, and its different 
members which include in descending order :— 
6.—The Water Lime formation 
5.—The Onondaga formation 
4.—The Guelph formation 
3.—The Niagara formation 
2.—The Clinton formation 
1.—The Medina formation 
