DESCRIPTION OF THE FORMATIONS. F\ 09 



( Fenestella shale, 15 feet. 



Hamilton I Tropidoleptus shale, 15 " 



upper ^ Barren shale, 200 " 



shale. j Paracyclas shale, 2 " 



{ Montebello fossil ore, 2 " 



Hamilton Montebello upper sandstone. 



The two uppermost of these beds have proved the 

 richest fossil iferous strata in the county, having yielded 

 more than a hundred species of fossils described and unde- 

 scribed. No clear line of demarkation can be drawn be- 

 tween them, the upper being marked in most places by a 

 profusion of Fenestella, especially near the top ; and the 

 lower by an abundance of the fossil from which it derives 

 its name. This species is not, however, confined to one 

 horizon. It ranges down into the Hamilton sandstone, in 

 the upper layers of which it is exceedingly abundant. In 

 the intermediate Barren shales few or no fossils can be found ; 

 and in the Paracyclas shales below them the species differ 

 largely from those in the uppermost bed, Paracyclas Virata 

 being the more characteristic form. The iron ore will be 

 described elsewhere. 



No. VIII d. Genessee group. 



This group was not recognized until a late date in the 

 work, and its barrenness renders its identification difficult. 

 Lying, however, as 200 feet of black, almost unfossiliferous 

 shale, between the fossiliferous Hamilton upper shale and 

 Portage shale, its place became evident as soon as those were 

 identified, and by this means it was traced over the county. 

 Its lower beds yield the Genessee species Styliola fissurella 

 near New Bloomrield. Its total thickness is not more than 

 200 feet. 



No. VI He. Portage group. 



Like the Genessee, these rocks were among the last identi- 

 fied, but are very constant, and their fossils sufficiently 

 abundant to occur at most localities. The commonest and 

 one of the most characteristic is the Cardiola (Avicula) 

 speclosa. described by Prof. Hall, from the Genessee of 

 New York. Other species also occur, some of them ap- 



