OUTLINE OF THIS PAPER. 



This work is a review, by one who is working in the Cambrian field, of the work of 

 his predecessors, and of the resnlts they and he have thus far obtained as he interprets 

 them. It thus becomes historical and descriptive, and is a general statement of the 

 principles upon which the correlations have been made in establishing the group. 



Chapter I gives a statement of the principles upon which the delimitation of the 

 group is based, a few brief remarks upon the nomenclature of the formations, and a 

 list of the books and articles consulted in the preparation of this paper. 



Chapter n gives a historical review of the geologic and paleontologic work that 

 has been done in the four provinces in which the sediments of the Cambrian group 

 occur. These are the Atlantic Coast Province; the Appalachian Province, which is 

 divided into the Northern Appalachian and Southern Appalachian areas; the Rocky 

 Mountain Province, and the Interior Continental Province. The latter is divided 

 into the Upper Mississippi Area, the Eastern Border or Adirondack sub-Province, the 

 Western Border or Rocky Mountain sub-Province, and the Southwestern sub-Prov- 

 ince of Texas and Arizona. Within each of the provinces the historical data are re- 

 viewed by the political divisions of States and Territories, and in British North 

 America by provinces. 



The historical review of the geologic work embraces all that has come within the 

 knowledge of the writer of the descriptive geology of the rocks now referred to the 

 Cambrian group. The paleontologic review includes only the mention of the genera 

 and species described by the various authors. 



Chapter in is a record of the names that have been employed to designate various 

 formations. It is of an historical rather than a controversial character. 

 s. Chapter iv gives a summary of the present knowledge of the formations in each of 

 the four geologic provinces, in the same arrangement as that of the historical review 

 in chapter II. The attempt is made to give a concise statement of the present knowl- 

 edge of the formations referred to the Cambrian group within each province. The 

 paleontologic references are to the larger subdivisions of the fauna without mention 

 of genera or species. These will be described in special monographs, now in the 

 course of preparation. At the close of this summary there is a synopsis of the Cam- 

 brian group, in which it is stated that the group is established by (a) the presence 

 in the Rocky Mountain Province of 6,000 feet of limestone with an undetermined 

 mass of quartzite beneath ; (b) in the Appalachian Province by over 12,000 feet of 

 quartzite, shales, slates, and limestones; (c) a continental distribution; (d) a charac- 

 teristic, highly differentiated fauna. A table of the classification of the formations is 

 arranged with the type formation of each subdivision at the head, while beneath 

 are the formations correlated with it. 



A map showing the geographic distribution accompanies this chapter ; also one 

 on which the sedimeutation is illustrated by vertical columns of strata. A section 

 across the continent, with the base of the Ordovician fauna as the upper limit and 

 the columns of strata arranged beneath it, reveals the presence of a great trough 

 along the line of the Appalachians from Alabama to Labrador, and a second trough 

 on the western side of the continent west of the eastern Rocky Mountain ranges. 

 It is claimed that the great interior Continental Province was a land area during 



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