C. D. Walcott — The Taconic System of Emmons. 327 



the "Lower Taconic," as stated in the scheme of 1856. (See 

 fig. 10.) 



The comparisons made by Dr. Emmons between the fossils 

 of the " Black Slate " and the Primordial fauna of Barrande, in 

 1859, came too late to anticipate the identification of the Prim- 

 ordial fauna in the Cambrian of Sedgwick, for the Cambrian 

 System, as used by me, was correctly identified, paleontolog- 

 ically, by M. Barrande, in 1851.* 



As I have repeatedly stated, Dr. Emmons assigned the two 

 species of fossils described by him from the " Upper Taconic " 

 slates to a pre-Potsdam horizon, on stratigraphic evidence that, 

 on investigation, proves to have been based on errors of field ob- 

 servation. Such being the case, there was no proof of the posi- 

 tion of the fauna, as he had no means for comparison with a 

 similar fauna that had been stratigraphically located elsewhere in 

 the geologic series. It was a fortunate happening that the " Up- 

 per Taconic " fossils proved to be of pre-Potsdam age, and not 

 a scientific induction based on accurate observations or compari- 

 sons. 



M. Barrande visited England in 1851 and determined the 

 age of the Primordial fauna found in the typical Cambrian 

 area of Wales before he knew of the existence of the vestige of 

 the Primordial fauna published by Dr. Emmons. Subse- 

 quently, upon the evidence of Dr. Emmons's published strati- 

 graphic sections, showing that he, Dr. Emmons, knew the 

 fossils to be stratigraphically pre-Potsdam, M. Barrande was 

 misled into crediting him with a discovery (in 1859) that was 

 based on errors of field observation, and I did the same thing 

 in the introduction to Bulletin 30, U. S. Geological Survey, in 

 1885. 



* January 20th, 1851, M. J. Barrande read a paper before the Geological So- 

 ciety of France, upon the " Silurian Terrain of England." He presented a sketch 

 of a section from Wales showing the Archean and, resting upon it, the stages 

 corresponding to the stages C and D, of the Bohemian section, or the strata of the 

 First or Primordial fauna and the Second or Lower Silurian fauna. Above the 

 Lower Silurian the Upper Silurian is shown as resting unconformably upon the 

 latter. In this paper the Lower Cambrian of Sedgwick is identified by organic 

 remains, through comparison with the established succession of fossils in the 

 Bohemian Basin. (Bull. Soc. G-eol. de France, t. viii, pp. 207-212, 1851). 



[To be continued.] 



