NATURAL HISTOKY, 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 limestone 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 

 Jialli, Calapoccia canadensis, Maclurea logani and 

 Gonioceras 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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