STRATIGRAPHIC SUMMARY. 605 



A. THE PALEOZOIC SYSTEMS. 



I. The Cambric System. 



General Subdivisions. — The Cambric of North America admits 

 of the following subdivisions •} 



Cambric or Taconic. 



Upper Cambric or Bretonian. (Including all except 

 the highest beds of the Bretonian of Matthew's St. 

 John Group, as well as the upper half of the Johan- 

 nian. The Potsdamian and Saratogan represent the 

 upper part only of the Bretonian in this sense.) 

 Middle Cambric or Acadian. (In the sense generally 

 used by the U. S. Geological Survey. Includes the 

 Acadian and lower half of the Johannian of Matthew's 

 St. John Group.) 

 Lower Cambric or Etcheminian (for the Atlantic 

 coast development). Georgian (for the Pacific coast 

 and Appalachian development). 

 Two main provinces are recognized : the Atlantic and the Pacific. 

 The typical sections for the Atlantic province are found in New 

 Brunswick, Cape Breton and eastern Newfoundland, where the 

 following subdivisions are recognized (Matthew) : 



Superformation. 



Basal Ordovicic shales. 

 Upper Cambric. 



12. Asaphellus homfreyi zone. 



II. Dictyonema flabelH forme zone. 



10. Peltura scarabeoides zone. 



9. Parabolina spinulosa zone. 



8. Agnostus pisiformis zone. 



Middle Cambric. 



7. Paradoxides forchhammeri zone. 

 6. Paradoxides davidis zone. 

 5. Paradoxides eteminicus zone. 



^ Grabau, A. W., Science, N. S., Vol. 39, pp. 351-356, 1909. , 



