DEVONIAN AND OLD RED PERIOD. 



17 



Generalised Section of the Devonian Rocks of 

 North America. 



Fig. 76. 



ooOOoOOOoO 



V: :\'t ';-/'•: ;Trtr"ff^';<<^>' 



000 o o O ^» *» o 



Catskill Group. 



Chemung Group. 

 Portage Group. 



Hamilton Group. 



Corniferous Limestone. 



Schoharie Grit, 

 Cauda-Galli Grit. 

 Oriskany Sandstone. 



Lower Helderberg. 



also yielded traces of many other plants (such as Annularia, 

 Aster ophyllites, Cardiocarpon^ &c-)? which acquire a greater pre- 

 dominance in the Carboniferous period, and which will be 

 spoken of in discussing the structure of the plants of the Coal- 

 measures. Upon the whole, the one plant which may be con- 

 sidered as specially characteristic of the Devonian (though not 

 confined to this series) is the Psilophyton (fig. 77) of Dr Daw- 

 son. These singular plants have slender branching stems, 

 with sparse needle-shaped leaves, the young stems being at 

 first coiled up, crosier- fashion, like the young fronds of ferns, 

 whilst the old branches carry numerous spore-cases. The 



