﻿Geological Map, District about Montreal. 249 



comprises the gray sandy shales of a considerable area 

 south of the St. Lawrence. 



2. Utica, black or brown shales. These occur along the 

 south shore of the St. Lawrence Kiver, near Montreal, and 

 extend to the upper part of the River Richelieu. 



3. Trenton, which consists chiefly of limestones and 

 black slates. They occur at Montreal, Philipsburg, Farn- 

 ham and other points on both sides of the St. Lawrence. 



4. Chazy limestones, conglomerates and slates south 

 and west of Montreal ; also at Mystic and Cowansville. 



5. Calciferous, which is closely associated with the 

 Chazy, and resembles it in character. They contain some- 

 what different fossil remains. 



6. Potsdam sandstone of 11^ Perrot and Beauharnois. 

 CUMBRIAN. — This system is largely developed in the 



eastern part of the area, especially in connection with the 

 older series of the Eastern Townships. 



The HuRONFAN, which forms the Sutton and Stoke 

 mountain ranges of the same section. 



The Laurentian, which occupies the mountainous dis- 

 trict which occupies the north-western part of the sheet. 



It will be noticed that both Calciferous and Potsdam 

 have been classed with the Cambro-Silurian system. The 

 latter is usually regarded as a part of the Cambrian. Con- 

 cerning this change in classification, Dr. Ells says (p. 50) : 

 " It may, however, be said that, in view of all the evidence, 

 both palcTeontological and stratigraphical, it has been con- 

 sidered most in accordance with the facts to regard the 

 Potsdam sandstone formation, as developed in the St- 

 Lawrence and Lower Ottawa areas, as the continuation 

 downward of the Calciferous, and to consider these two 

 members as constituting the basal portion of the Cambro- 

 Silurian system. No defined break between the Calciferous 

 limestone and the Potsdam sandstone has yet been 

 observed in Canada." 



The map shows the railways and roads as well as the 



