292 



PALAEOZOIC TIME DEVONIAN AGE. 



The formation, instead of thickening to the westward in New 

 York, like those preceding it in time, thins out in that direction, 

 and thickens towards the Hudson, heing two or three thousand 

 feet in the Catskills. It stretches south along the Appalachian 

 region, beneath the Coal formation of Pennsylvania and Virginia, 

 where it is 5000 or 6000 feet thick. It is eminently an Appalachian 

 formation. 



II. Life. 



The rocks afford but few relics of animal life, and these differ 

 completely from those of the earlier periods. There is thus, as 

 appears, a new beginning in the life of the continent. It is, how- 

 ever, yet uncertain what were the condition and life of the interior 

 region, as no strata have been there recognized as certainly of 

 this era. 



1. Plants. — The land-plants, relics of which are occasionally met with, were 

 of the same Carboniferous character as in the Chemung period. Fig. 507 A 



Fig. 508. 



Modiola angusta. 



represents a portion of a large frond of the Noeggerathia obtusa, from Montrose, 

 Pa., — a characteristic fern of the period. The frond was over a foot broad. 



Figs. 509-511. 



Fig. 509, Holoptychius Americanus ; 510, Tooth, id. ; 510 a, section of same tooth ; 

 511, Holoptychius Taylori. 



2. Animals. — Among animals, no Corals, Crinoids, Brachiopods, or Trilobites, are 

 yet known. There are some Conchifers, such as (fig. 508) the Modiola angusta 



