2o4 



PALEOZOIC TIME. 



II. AGE OF FISHES, OR DEVONIAN AGE. 



The Devonian formation was so named by Murchison and Sedg- 

 wick, from Devonshire, England, where it occurs, and abounds in 

 organic remains. In America, and also in other countries, the beds 

 pass into those of the Silurian by an easy transition. 



1. American. 



The periods and epochs in the American Devonian, as deduced from 

 the series of rocks laid down by the New York geologists, are the 

 following, commencing above : — 



4. Catskill Period (12) . 

 3. Chemung Period (11) . 



2. Hamilton Period (10) . 

 1. corniferous period (9). 



{■ 



. Catskill Red Sandstone (12). 



2. Chemung Epoch — Chemung group (11 b). 



1. Portage Epoch — Portage group (11 a). 



3. Genesee Ejjoch — Genesee beds (10 c). 



2. Hamilton Epoch — Hamilton group (10 b). 

 Marcellus Epoch — Marcellus group (10 a). 



3. Corniferous Epoch — Upper Helderberg group 



(9 c). _ 

 2. Schoharie Epoch — Schoharie grit (9 b). 

 1. Cauda-galli Epoch — Cauda-galli grit (9 a). 



The beds of the first period are sometimes designated the Lower 

 Devonian, and those of the second, third, and fourth periods, the 

 Upper Devonian. The Corniferous period was the great limestone- 

 making period of the Devonian age in America. The rocks of the 

 succeeding periods (Upper Devonian) are mostly shales or sandstones, 

 with only subordinate layers of limestone. 



1. CORNIFEROUS PERIOD (9). 

 Epochs. — 1. Cauda-galli, or that of the Cauda-galli grit (9 a) ; 

 2. Schoharie, or that of the Schoharie grit (9 b) ; 3. Corniferous, 

 or that of the Onondaga and Corniferous limestones (9 c). 



I. Rocks: kinds and distribution. 



The rocks in New York, of the first two divisions of the Corniferous 

 period, are sandstones or gritty shales. Like the beds of the pre- 

 ceding period, they have their largest development along the Appa- 

 lachian region. But the Cauda-galli grit, unlike the Oriskany sand- 

 stone, lies in the eastern half of the State of New York, and thickens 

 toward the Hudson, being fifty or sixty feet thick in the Helderberg 

 Mountains. The Schoharie grit, named from its occurrence in Scho- 

 harie, N. Y., has nearly the same distribution ; and the rock is much 

 like the preceding, though very different in its fossils. The term 

 Cauda-galli alludes to the feathery forms of a common fossil, supposed 

 to be a sea-weed (Fig. 484). 



