526 C. SCHUCHERT PALEOGEOGRAPHY OF NORTH AMERICA 



and it is a remarkable fact that on the two sides of the ocean these faunas 

 should be so much alike. 



The principle of diastrophism combined with these guide fossils has 

 convinced Ulrich and the writer that they can no longer subscribe to the 

 generally accepted delimitation of the Ordovician or Lower Silurian sys- 

 tem. It will be here shown that this period had three cycles of sea move- 

 ments. In other words, there were three submergences of Xorth Amer- 

 ica, two great and one small, each of which was followed by a small or a 

 very marked emergence. This so-called system may therefore be divided 

 into three periods — the Canadic, the Ordovicic, and the Cincinnatic. 



Canadic Period (new: Ulrich) 



(In part Calciferous. Canadian, or Beekinantown of geologists) 



See plates 54 and 55. and pages 485, 4S6 



As far as published work is concerned, a great deal of obscurity exists 

 regarding the relationship and distribution of the formations composing 

 the Canadic series. Ulrich has studied these deposits in most regions 

 throughout the United States, and in this volume he presents a digest of 

 the information thus acquired. He and the writer jointly herewith give 

 two paleogeographic maps, one showing the time of greatest transgression 

 and another the emergence about half completed. 



This period or system is bounded below by the Ozarkic and above by 

 the Stones Eiver-Chazy series of the Ordovicic. The type area for this 

 period of the Mississippian sea is lake Champlain of northeastern New 

 York. Of Brainerd and Seely's 1 * 8 Calciferous section, it embraces their 

 divisions C, D, and E (not their A and B, which belong in the Ozarkic 

 period) . Combined, these divisions have a thickness of about 1,200 feet. 

 The fauna has been described by Whitfield 149 and Buedemann. 150 With 

 divisions A and B, these compose the Beekmantown of Clarke and 

 Schuchert. 151 The section downward is as follows : 



E. Thin-bedded magnesian limestone, 470 feet thick. Has Helico- 

 toma similis, Murckisonia confusa, Bucania ( ?) triplet. BathyitreUus 

 glandicephalus, Primitia seeleyi, P. cristata, P. gregaria. Orthoceras per- 

 seus, and 0. xerxes. 



D4. Thin-bedded blue limestone alternating 1 with slatv ] avers. 100 





148 Brainerd and Seely : Bull. American Museum of Natural History, vol. 3, 1890, pp. 

 1-23. 



149 Whitfield : Ibidem, vol. 1. 1886, pp. 293-345. Ibidem, vol. 2. 1889, pp. 41-65. 

 Ibidem, vol. 3, 1890, pp. 25-39. 



150 Ruedemann : Bull. 90. New York State Museum, 1906. 

 ™ Clarke-Scbuebert : Science, 1899. p. S78. 



