SILURIAN 355 



In a report on his exploration of the country from Lake Winnipeg to 

 Hudson Bay, Low^^ described limestones or dolomites having a total 

 thickness of not more than 100 feet, the fossils of which he regarded as 

 not* older than the Galena and possibly as young as the Niagara. Dow- 

 ling^^ noted horizontal limestones along Ekwan Eiver, between 33 and 

 100 miles above its mouth. He recognized the coral reef mentioned by 

 Bell along Atiawapiscat Eiver. He collected a few fossils which were 

 identified by Whiteaves, who thought the horizon they represented was 

 rather high in the Silurian. 



In the report on the Algoma and Thunder Bay districts, Ontario, there 

 is given a list of fossils collected by W. J. Wilson^^ from the Nagagami 

 and other branches of the Kenogami Eiver, and identified by Whiteaves, 

 who thought they indicated the Silurian age of the rocks from which they 

 came. 



In 1910 Mclnnes^^ described the structure and character of the rocks 

 exposed on Winisk Eiver. The Silurian age of these strata was deter- 

 mined by Whiteaves on the basis of seven species of fossils that he was 

 able to identify of those collected by Mclnnes from that region. 



TyrrelP* described limestones exposed along the Severn and Fawn 

 rivers and gave a list of fossils from them, which were identified by 

 Parks, on the basis of which their age was considered approximately that 

 of the Guelph of eastern Canada. 



PRE8E^'T STUDIES 



The oldest Silurian rocks in the region outcrop about 4 miles below 

 the Lower Limestone Eapids on Nelson Eiver, described in the section of 

 rocks exposed along that river under the name of Port Nelson limestone. 

 At this place a thickness of 28 feet of rather even-bedded, yellowish dolo- 

 mite is present above the level of the water. Only a few fossils were 

 found in the exposed part of this ledge, but farther down the river numer- 

 ous fresh fragments of fine-grained, yellow dolomite crowded with shells 

 of Virgiana decussata and other fossils indicate that this zone of the 

 Silurian is present along the river, probably at a little lower horizon than 



i** A. P. Low : PreliminaiT report on an exploration of the country between Lake 

 Winnipeg and Hudson Bay. Geol. Survey of Canada, Summary Rept., 1886, p. 18F. 



11 D. B. Dowling : Report on an exploration of Ekwan River, Sutton Mill lakes, and 

 part of the west coast of James Bay. Geol. Survey of Canada, Summary Rept., 1901, 

 pp. 1-60F. 



12 W. J. Wilson : Report on a portion of Algoma and Thunder Bay districts. Geol. 

 Survey of Canada, 1909, pp. 34-41. 



13 "W. Mclnnes : Report on a part of the Northwest Territories drained by the Winisk 

 and Attawapiscat rivers. Geol. Survey of Canada, 1910, pp. 1-54. 



1* J. B. Tyrrell : Report on the Hudson Bay exploring expedition. 22d Ann. Rept. 

 Ontario Bureau of Mines, 1912, pt. 1, pp. 161-209. 



XXV — Bull. Geol. Soc. Am.. Vol. 30. 1918 



