164 PALEOZOIC TIME. 



2. Utica Epoch (4 b). Utica shale. 



3. Cincinnati Epoch (4 c). (Hudson River epoch of last 



edition of this work.) Part of Hudson River shales, Lorraine 



shales, of New York ; limestone of Cincinnati ; Nashville group 



of Tennessee. 



In Great Britain, Bala limestone and Caradoc sandstone; upper part of Llaiy 

 deilo flags; Lower Llandovery sandstone. In Bohemia, Barrande's formation D 1 . 

 In Sweden, Graptolitic slate; Angelin's Region D. In Russia, the Wesenberg, 

 Lyckholm, and Bornholm groups. 



B. UPPER SILURIAN. 

 I. Niagara Period (5). 



1. Medina Epoch (5 a) : Oneida conglomerate and Medina 

 sandstone. 



2. Clinton Epoch (5 b) : Clinton group. 



3. Niagara Epoch (5 c) : Niagara shale and limestone ; 



Guelph limestone. 



In Great Britain, the Upper Llandovery or May Hill sandstone has been 

 referred to the Clinton and Medina, and the Wenlock shale and limestone to the 

 Niagara. In Sweden, part of Region E of Angelin, and, in Bohemia, Stage E of 

 Barrande are probably equivalents of the Medina, Clinton, and Niagara. The 

 Pentamerus group of Esthland and Livland in Russia, and the Lower Malmo of 

 Norway are referred to the Medina and Clinton, and the middle Malmo to the 

 Niagara. 



II. Salina Period (6). Onondaga Salt group. 



III. Lower Helderberg Period (7). 



Lower Helderberg limestones, including, in New York, (1) the 

 Water-lime group ; (2) the Lower Pentamerus limestone; (3) the 

 Delthyris shaly limestone ; (4) the Upper Pentamerus limestone. 



IV. Oriskany Period (8). — Oriskany sandstone. 



In Great Britain, the equivalents of the Lower Helderberg and Oriskany groups are 

 approximately the Ludlow beds, including the Lower Ludlow rock, the Aymestry lime- 

 stone, the Upper Ludlow rock and the Tilestones. In Norway, Upper Malmo limestones 

 and schists. Part of E of Angelin, in Gothland, Sweden, the Coral limestone. In Bohe- 

 mia, Barrande's formations E to H, consisting of schists, part graptolitic, and limestones, 

 are referred to the Upper Silurian. 



Explanation of the Section and Geological Map. 

 The annexed map of New York and a part of Canada exhibits the 

 surface-rocks of the region. As is shown in the section, p. 166, the 

 strata of the Silurian and Devonian outcrop in succession, on going from 

 the Archaean (No. 1) southward. The numbers on the areas render easy 

 a comparison with the section and with the tables beyond. The Si- 

 lurian strata are lined horizontally ; the Devonian, vertically ; and the 

 Subcarboniferous beds, which appear at the southern margin of New 

 York State (No. 13), are cross-lined. The area very coarsely cross- 

 lined horizontally includes the Chazy and Trenton limestones ; the 

 Chazy (3 c) is separated from the Trenton by a dotted line. 



