MINERALS AND GEOLOGY OF CANADA. 445 
The best and almost the only known exposures occur in the township 
of Bosanquet in the north-west corner of the county of Lambton. 
As there seen, its strata are composed of soft grey calcareous shales, 
“with one or two beds of encrinal limestone. Sir William Logan esti- 
mates the total thickness of the formation, with us, at about 300 feet. 
The shales contain numerous fossils, the most abundant, perhaps, 
‘being the four species figured below.* 
a Fig. 238. Fig. 239. 
Spirifer mucronatus Spirigera concentrica 
(Conrad), (Von Buch). 
Fig. 240. Fig, 241. 
Airypa reticularis Orthis Vanuxemi 
(Linnzeus). (Billings). 
In addition to these, several corals and some other brachiopods are 
of common occurrence; and examples of the trilobite, Phacops bufo, 
fir, 237, are often met with. 
Petroleum Springs and Wells.—As stated on a preceding page, the 
celebrated ‘ oil-wells’? of Western Canada are principally situated 
within the area occupied by the Hamilton shales, although the oil 
itself, more properly known as petroleum or fluid bitumen, is thought 
to arise from the underlying Corniferous formation. The existence 
* These species occur also abundantly in the Corniferous formation; and Atrypa reticu= 
Jaris is found as low down as the Clinton group. 
