DEVONIAN AGE. 



277 



In this section, from one by Hall, taken in Yates County, N. Y., 10 a, 10 b, 10 c are 



Fig. 550 B. 



116 



10 a 



Section of rocks of the Hamilton and Chemung Periods. 



rocks of the Hamilton period; a, the Marcellus shale; b, the Hamilton group; c, the 



Genesee shale; and, in the Hamilton group, 2 is the Encrinal limestone, and 4 the Tully 



limestone; 11 a is the Portage group, 11 b the Chemung group. 



Westward of New York, the Portage and Chemung groups are continued into Ohio, 



just along the south side of Lake Erie ; and the Black shale of Ohio and the States west 



and south, is regarded by Newberry as partly of Portage age. 



I 



II. Life. 



The fossils of the Chemung period are almost wholly different in 

 species from those of the Hamilton. 



1. Plants. 



Besides the Cauda-galli and other Sea-weeds, there are remains of 

 many land-plants. They are, in genera, like those of the preceding 

 jperiod. Some of the kinds are here represented. 



Figs. 551-554. 



Plants. — Fig. 551, Cyclopteris Halliana; 552, Sigillaria Vanuxemi ; 553, Lepidodendron Chemun 

 gense. Brachiopod. — Fig. 554, Atrypa hystrix. 



A large-leaved fern, from the Chemung of Gilboa, N. Y., is named by Dawson Cyclop- 

 teris Gilboensis. The form somewhat resembles Fig. 557 A, p. 279, of a Catskill species. 



