156 Dr. H. Hichs — Cambrian Rocks of iV^. America. 



and the facts which have been obtained are particularly interesting 

 to British geologists. Two recent communications by Mr. C. D. 

 Walcott, Palgeontologist to the U. S. Geological Survey, are especially 

 deserving of study in reference to the classification of these rocks/ 

 and many facts of importance bearing on the same question are also 

 given in papers by Mr. G. F. Matthew, of St. John's, N.B.* 



That the classification found most suitable by the majority of those 

 who have, during recent years, studied these rocks in Great Britain 

 should now have been adopted by such experienced geologists in 

 America, is very strong evidence of its wide applicability, and is a 

 fact which should, I think, have influence on those who still hesitate 

 in adopting it as the best means of bridging over the insuperable 

 difficulties connected with the classifications of the rival schools of 

 Sedgwick and Murchison. 



In his introductory observations Mr. Walcott says,^ " In using the 

 name Cambrian in this paper for the series of strata characterized by 

 the First or Primordial fauna of Barrande, I do not forget the claims 

 of the name ' Upper Taconic,' which Dr. E. Emmons proposed for 

 the strata now placed under the Middle Cambrian or Georgia 

 Formation," and, " The term Cambrian is used from the belief that 

 in so doing I approve of the view of those writers who hold that 

 each of the distinguished authors, respectively, of the names Silurian 

 and Cambrian will be fairly recognized, and geologic nomenclature 

 advanced by the use of the names Cambrian and Silurian for the 

 divisions of strata characterized hy the first and third faunas as 



defined by Barrande Of the presence of a well-defined 



geologic sj'stem beneath the strata characterized by the second fauna 

 of Barrande or the Trenton fauna (including the Chazy and most of 

 the Calciferous) of North America, on the North American continent, 

 there is no question. The geologic sections given in this paper show 

 it to have a total thickness of over 18,000 feet, and that its middle 

 division has a known fauna of 43 genera, represented hy 107 species. 

 We also know that the Lower Cambrian or Paradoxides fauna has 

 32 genera and 76 species ; that the Upper Cambrian or Potsdam 

 fauna includes 52 genera and 212 species ; that of the 393 species 

 now known from Cambrian rocks but very few pass up into the 

 Calciferous horizon of the Lower Silurian (Ordovician) ; and that 

 the faunas of the two systems are so distinct in their general facies, 

 and also in detail, that they are quite as readily separated as the 

 Silurian and the Devonian or the Devonian and the Carboniferous. 

 There is no doubt that in certain areas the faunas of the Cambrian 

 and the Lower Silurian (Ordovician) systems are intermingled; but 

 the same is more or less true of all the great divisions of the entire 

 geologic series from above the great Archgean break to the Quater- 

 nary." 



' " Classificatioii of the Cambrian System of North America," Amer. Journal of 

 Science, vol. xxxii. and "Bulletin of the United States Geolog. Survey, No. 30," 

 1886. 



2 " Illustrations of the Fauna of St. John's Group," Trans. Royal Soc. Canada, 

 1885, and '' On the Cambrian Faunas of Cape Breton and Newfoundland," Canadian 

 Eecord of Science, Oct. 1886. ^ Bulletin U.S. Geolog. Sui'vey, No. 30, 1886. 



