228 New York State Museum 



America and its waters spread across the continent and 

 even entered the Appalachian trough, which therefore 

 belonged to the Pacific Province. The Atlantic Prov- 

 ince was separated from the Appalachian trough by the 

 land mass of Appalachia which appears to have ex- 

 tended through the center of Newfoundland since de- 

 posits of the Pacific Province are here found in the 

 western part and those of the Atlantic Province in the 

 extreme east. 



Trilobites were the dominant form of life of the Cam- 

 brian and made up the largest element of the fauna, the 

 brachiopods holding second place. So characteristic 

 are the trilobites that their names have been used to 

 indicate the divisions of the systems which they char- 

 acterize, as Lower Cambrian or Olenellus fauna, Mid- 

 dle Cambrian or Paradoxides fauna, Upper Cambrian 

 or Dicellocephalus fauna. This is to a certain extent 

 misleading and must be qualified since some genera 

 are characteristic of the Pacific Province and others of 

 the Atlantic Province. In the Pacific Province the 

 Lower Cambrian is characterized by species of Olenel- 

 lus, the Middle Cambrian by Olenoides and the Upper 

 Cambrian by Dicellocephalus ; while in the Atlantic 

 Province the equivalent divisions are characterized re- 

 spectively by Holmia, Paradoxides and Olenus. 



The fact that in the Cambrian are representatives of 

 the highest forms of invertebrates, the crustaceans, in- 

 dicates that life was well-developed before the Cam- 

 brian and must have developed in that period of time 

 between the Proterozoic and Cambrian which has left 

 no depositional record on our present land areas, and 

 is marked by a practically universal unconformity. 

 Plants must have been in existence in large numbers 



