NATURAL HISTORY, TORONTO REGION 
at Longford, south of Washago, near the northern 
branch of the Grand Trunk Railway on Lake Couchi- 
ching, and also at Kingston, at the east end of Lake 
Ontario. 
The Jimestone may rest immediately on the 
steeply tilted gneiss, or there may be a thin sheet of 
coarse sandstone or conglomerate at the bottom. 
There is no doubt that the Black River beds once 
extended farther north and are now being stripped 
from the older crystalline rocks, exposing once more 
the Pre-Cambrian continental surface. 
The Black River limestone is used for building 
stone and for lime-burning. It is not highly fos- 
siliferous, the commonest fossils being Columnaria 
hall, Calapoccia canadensis, Maclurea logani and 
Gomtoceras anceps. 
Immediately above the solid limestones mentioned 
above there is often a limestone formed in thinner 
sheets with partings of shale, the Trenton limestone. 
This occurs on the east side of Lake Simcoe, along 
Trent River, and at several points on the shore of 
Lake Ontario, such as Cobourg, Port Hope and 
Trenton. It is much thicker than the Black River 
and is richer in fossils. The beds are so gently tilted 
that they appear horizontal to the eye, but by com- 
paring the same horizon at different points a dip 
toward the southwest of thirty or thirty-five feet to the 
mile has been found. 
The following fossils are frequently found in the 
Trenton rocks: 
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