322 MINERALS AND GEOLOGY 



it is thought that the petroleum of this part of the region has been 

 brought towards the surface by fissures resulting from these anti- 

 clinals. A transverse or nearly north and south fold, forming a trough 

 or synclinal filled with higher Devonian strata (of the Hamilton or 

 Lambton formation), also occurs in the south-western portion of the 

 district between Lake Erie and the south point of Lake Huron. 



The Niagara Formation in this district, is made up of dark -gray 

 calcareous shales and thick-bedded limestones, both of which are more 

 or less magnesian and bituminous. Its lower limit is regarded, con- 

 ventionally, as indicated by a magnesian limestone holding shells of 

 the brachiopod Pentamerus oblongus (fig. 19 ) ; but this " Pent- 

 amerus bed " is referred by the New York geologists to the upper 

 part of the underlying Clinton formation. At Niagara Falls, the 

 dark shales present a thickness of about 80 feet, and form the lower 

 portion of the escarped face over which the cataract breaks, whilst 

 the upper portion of the cliff is composed of thick-bedded limestones. 

 Along the gorge, the shales are mostly concealed by the slope or 

 talus of detrital matter which rests against the cliff face ; but they 

 may be seen on the side of the steep road which leads from the old 

 ferry to the Clifton House, and at several other spots. Some of the 

 beds of this formation yield excellent hydraulic lime, much of the 

 " Thorold cement " being manufactured from the lime obtained from 

 them. Many of the Niagara beds are rich in fossils. The more 

 common species comprise : The corals : Favosites Gothlandica (=F. 

 Niagarensis fig. 137J; and Haly sites catenulatus (the so-called 

 "chain coral" fig. 139); the Bryozoon, Fenestella elegans (fig. 181) ; 

 the Brachiqpods : Pentamerus oblongus (fig. 193); Orthis elegantula 

 (fig. 197) ; Spirifer Niagarensis and S. radiatus (fig. 184); and the 

 Trilobites, Calymene Blumenbachii (ranging upwards from earlier 

 strata, fig. 167, 178); Homalonotus delphinocephalus (fig. 179) and 

 Dalmannites limulurus (fig. 175). The formation extends a few 

 miles westward from the edge of the great line of escarpment 

 already described as running from the Niagara River, by Hamilton, 

 Georgetown, etc., to Cabot's Head on Georgian Bay and then passes 

 under the succeeding Guelph formation. It thus marks the eastern 

 and northern limits of the table-land of which the Erie and Huron 

 district largely consists. Good exposures occur more especially at 

 the Niagara Falls and 011 the adjacent banks of the river (where the 



