as 
On the Geology of the Northwestern Regions of America. 327 
length of Mackenzie River as far as the shores of the Arctic Sea. 
Springs and pits of fluid bitumen are of common occurrence, and 
along the banks of Elk River in particular the shale beds are so 
saturated with this mineral as to be nearly plastic. The whole 
formation bears a decided resemblance in its lithological character 
to the lower members of the “Erie Division” of the United 
States’ geologists, which M. de Verneuil considers to be equiva- 
lent to the Devonian formation of Europe*. I have been enabled, 
through the kindness of Mr. S. P. Woodward, to examine the 
collection of fossils from this district in the British Museum ; and 
although, from the poverty of organic remains (a circumstance 
characteristic of the formation also in the United States), the col- 
lection is a very small one, there can be no hesitation in assigning 
the bituminous deposits of the, Elk and Mackenzie Rivers to the 
epoch of the Marcellus shales, and the associated limestones, of 
the New York Survey.” 
The most characteristic fossil of the bituminous beds is a small 
Pteropodous shell, thickly disseminated through the substance o 
the shale, apparently the Tentaculites fissurella of Hall, associa- 
ted with Strophomena mucronata, S. setigera, and Orthis limi- 
faris, of the same author; at least they cannot be distinguished 
from his figures of those fossils from the Marcellus shales 
Two corals from the associated bituminous limestone are, 
according to Mr. Woodward, characteristic of the same epoch, 
hamelyea Strombodes (of Hall), having its cysts filled with bitu- 
roductus (among them P. subaculeatus), an Orthis resembling 
9. resuptnata, T'erebratula reticularis, a Posidonomya, and a 
Pleurotomaria. ‘There is a very fine and well preserved Rhyn- 
chonella amongst the collection, remarkable for retaining the 
orginal chesnut-colored bands of the shell. 208 
ther Formations of the Mackenzie River Basin.—Silurian 
rocks of Great Slave Lake and River (Onondaga Salt Group 
Y Vanurem and Hali?),—After passing through Lake Athabasea 
the Elk River is joined by the Unjigah or Peace River, the largest 
y of the Mackenzie, and the united streams, under the 
Rame of Slave River, proceed onwards to Slave Lake along the 
edge of the district of crystalline rocks, flowing sometimes 
through limestone, at other times over granite, and sometimes 
between the two. he mouths of Slave River open into Slave 
*e between the limestone and granite. The limestones along 
the banks of this stream are, like those of the Elk River, highly 
bituminous ; but they are chiefly remarkable from their associa- 
ee With extensive beds of compact greyish gypsum, in connex- 
' * Bulletin Soc. Géol. Fr. 2 Sér. vol. iv, p. 646. 
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