CATSKILL PERIOD. 291 



Life. — In its plants the Chemung period indicates the approach 

 of the Carboniferous age, — the genera Lepidodendron, Sagenaria, 

 Sphenopteris, Catamites, being characteristic of that time. Its animal 

 species bear marks of new progress, in the great Goniatites, with more 

 complex septa, and the greater abundance of large-winged Spirifers, 

 as well as the occurrence of species having spinous shells. 



CATSKILL PEKIOD (12). 

 I. Rocks : kinds and distribution. 



The rocks of the Catskill period are shales and sandstones of 

 various colors, in which red predominates. The sandstones are far 

 more extensive than the shales, and pass into conglomerates or 

 coarse grit-rock, and also into a rough mass looking as if made of 



Fig. 507 A. 



Noeggerathia obtusa. 



cemented fragments of hard slate. The upper part is in general a 

 conglomerate. There are ripple-marks, oblique lamination, and 

 other evidences of sea-shore action, in many of the strata. Some of 

 the layers are partially calcareous. 



