278 



RECORD OF SCIENCE FOR 1886. 



Walcott, Charles Doolittle — Continued. 



A paper read before the National Academy of Scieuce at Washington, D. C, 



April 23, 1886. 

 Many of the data in this paper are taken from the introduction of Bulletin 30, 



U. S. Geol. Survey, by the same author. 



Walcott, Charles Doolittle. Walcott on the Cambrian of North 

 America. Amer. Jour. Sci., August, 1886. (Amer. Nat., vol. XX, 

 pp. 800-802, September, 1886. Philadelphia.) 



Abstract of. 



Walcott, Charles Doolittle. Classification of the Cambrian 

 SystcMn of North America. (Nature, vol. xxxiv, p. 402, 1886. Lon- 

 don and New York.) 



Notice of. See American Journal of Science, August. 



Walcott, Charles Doolittle. Classification of the Cambrian 

 System of North America. (Amer. Jour. Sci.. 3d ser., vol. xxxii, pp. 

 138-157, figs. 1-9, August, 1886. New Haven.) 



Much of the data given in this paper is embraced in the introduction to the 

 " Second Contribution to the Studies of the Cambrian Fauna'^ of North 

 America'' (Bulletin 30, U. S. Geological Survey), although, owiug to the 

 delay in the publication of the latter, it appeared four months earlier. 

 The most noticeable addition is the hypothetical map showing the land 

 area during the deposition of the Middle Cambrian Strata, the description 

 of its extent, and the disappearance of large portions of it just prior to the 

 deposition of the formations carrying the Potsdam faunas. This broad 

 generalization was developed by the study of the geographic and vertical 

 distribution of the Cambrian faunas. 



Walcott, Charles Doolittle. Second contribution to the Cam- 

 brian Faunas of North America. (Bull. 30, U. S. Geol. Survey, pp. 

 225, pis. i-xxxiii, 1886. Washington.) 



In this second contribution, Mr. Walcott has given a review of the strati- 

 graphy of the Cambrian system in the United States, and a description of 

 the faunas of the Middle or Georgia horizon of the Cambrian. 



In the introduction the principal geologic sections of the Cambrian system are 

 described and illustrated, and a general description of the Middle Cambrian 

 horizon and its relations to the Lower and Upper Cambrian are given, and 

 also the geographic distribution of the fauna on the North American con- 

 tinent. 



In a resume of the table of the Cambrian faunas of North America the follow- 

 ing table occurs (bottom of page 61) : 



Stratigraphic resume. 



Upper Cambrian . 

 Middle Cambrian 

 Lower Cambrian . 



Re-appearances . . 

 Total fauna 



