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lenticular cavities, and as usual destitute of organic remains. Its 

 elevation above the level of the river cannot exceed eight feet : its 

 extremely slight dip towards the north-west is perceptible. 



The overlying limestones are well seen on the western side of the 

 river, one mile from the village of Truago in Monguagon. The most 

 common variety of the rock at this place is a light grey, somewhat 

 sparry limestone, which becomes yellowish and mealy by weather- 

 ing. It strongly resembles the limestone of the Maitland, and that 

 seen in the bed of the Thames at Beachville. It has an inconsider- 

 able dip towards the north-west. The same strata are displayed in 

 a series of quarries on the Canada side, about two miles from Mai- 

 den. The dip here is scarcely noticeable : if any prevails, it is west- 

 ward. The Truago and Maiden beds manifestly overlie the vesicu- 

 lar rock of Gros Isle, and agree in their fossils with the similarly 

 placed limestone of the Maitland. They contain strophomena lineata, 

 another strophomena, atrypa affinis, also another atrypa, septsena, 

 orthoceratites, cyathophillum, ceratites, favosites, encrini, a trilobite, 

 and several fossils not yet determined. 



Rocks of the Maamee River and of Sandusky Bay. — On the 

 Maumee, in Ohio, the pitted limestone is again met with, under fea- 

 tures identical with those of the rock seen at Gros Isle and Gode- 

 rich. Its occurring thus so exactly in a line with the two last named 

 places, goes unequivocally to establish the anticlinal axis supposed to 

 pass from the western part of Canada into Ohio. This axis crosses 

 Lake Erie probably about midway between the head of the lake and 

 the chain of islands stretching from Point du Playe to Point Sandus- 

 ky. An examination of the fossils of the Sandusky limestone esta- 

 blishes beyond a question its identity with the formation exposed at 

 Maiden, Truago and Goderich. This agreement is the more interest- 

 ing, since the Sandusky rock, under the name of the cliff limestone 

 of Ohio, has by some geologists been regarded as the equivalent of 

 the European carboniferous or mountain limestone. But an inspec- 

 tion of its organic remains shows that its closest foreign relations are 

 to the Wenlock limestones of the English silurian strata. There 

 exists moreover in Tennessee and Virginia a higher limestone, not 

 seen in Ohio or New York, much more accurately referrible to the 

 European mountain limestone, and so regarded by Prof. Troost, in 

 his annual reports and other communications on the geology of Ten- 

 nessee. This rock, characterized by its oolitic structure, and the 

 beautiful genus pentremites, seems, from the descriptions given, to 

 overlie the cliff limestone of Ohio. 



