PHYSICAL ASPECT OF CAMBRIAN ROCKS IN EASTERN CANADA. 257 - 
make up the Hags and slates of the Johannian division (see be- 
low) glisten with water-born particles of mica, the sands are of 
uniform texture, and there are no traces of shore lines, though 
shallow water beds abound. 
Also the Bretonian division, with its fine grained dark gray 
mud beds holding graptolites, and the perfect preservation of its 
delicate organisms, indicate the presence of a water-cushion of con- 
siderable depth above its muds, when these were being deposited, a 
cushion which we can hardly think was less than i,ooo feet deep. 
But a sea of this depth would have covered a wide area along 
the Atlantic coast, and we therefore infer that the known basins 
of Cambrian rock are but small fragments of the wide spread 
mantle of sediments that covered this region at the beginning of 
Ordovician Time. 
The group of organic remains of the outer zone of the 
Etcheminian rocks appears to differ widely from that of the 
inner. This may be because they do not come from the same 
time-horizon ; but it seems more likely to be due to some physical 
cause, either difference in the depth of the sea in the two zones, 
or paucity or abundance of sediment in the waters, or difference 
of temperature of the sea water in the two zones. Whatever the 
cause, Olenelloid trilobites have not been recognized in the strata 
of the inner zone, while they are characteristic of the faunas of 
the outer zone. 
In the following catalogue the several districts where the 
fossils described in it were found are indicated by letters in the 
fourth column, viz. : 
A is eastern Massachusetts (Boston to Attleboro’). No fossils from 
this are mentioned, because the author’s work did not extend there. 
B is southern New Brunswick. The numbers following indicate the 
basin of this area where the fossil was found, numbered from N. W. 
to S. E. These basins once united, have been separated by crustal 
movements and great denudation. 
C is the peninsula of Nova Scotia. No characteristic fossils are known 
from this area. 
D IS Cape Breton. The basins of Cambrian rocks are indicated as those 
of New Brunswick by numbers. 
E is the area of Avalon in Newfoundland. The more important basins 
are indicated by numbers. 
