AND THE REPORT ON THE GEOLOGY OF VERMONT. 127 



by C. H. Hitchcock. In the first article Mr. ^Vliittiekl describes from the Georgia slates 

 the fossils found there, as far back as 1861 and 1862, by Jules Marcou, under the names 

 of Orthisina orientalis and DiTcelocephalusf Marcoui. He gives also a better figure and 

 description of Olenellus Thompsoni with the long caudal spine, from a specimen found 

 by Marcou ; and finally he adds a new trilobite Jbigelina HifcJwocli, also from Parker's 

 quarry. He regards the Georgia slates and even the limestone at Pointe-Levis as be- 

 longing to the tyiiical Potsdam, without saying if it is the Potsdam sandstone of the 

 village of Potsdam, or at Keeseville, or at any other locality in the state of New York. 

 Mr. Hitchcock describes several sections. His aiinnber " 6. Clay slates and argilitic 

 and other schists, supposed to be of Cambrian age. Of these, the Georgia slates of 

 the Vermont report contain the Olenellus and Angelina, etc." At p. 158, he says, " It is 

 just here that the fatal defect of the establishment of the Taconic system, as defined by 

 Emmons, exists. His palaeontological arguments were better than the stratigraphical." 

 Finally, Professor Hitchcock closes his article with some remarks on " Colonies," indors- 

 ing Logan's sections at liighgate Springs and Swanton, and the reality of his theory. 



1885 (Jan.). "The Taconic system and its position in stratigraphical geology," by 

 Jules Marcou, communicated December 10, 1881, to the American Academy (Proceed. 

 Amer. Acad. Arts and Sciences, new series, Yol. xir, p. 174, Cambridge), contains a 

 tabular view of the Taconic, p. 224, where the Georgia slates or Olenellus zone is placed 

 in the middle of the Taconic. And at p. 231, another tabular view of the Eureka sec- 

 tion by Mr. Walcott shows that the lower part of the Prospect Mountain limestone of 

 Nevada is regarded by Marcou, as the equivalent of the Georgia slates or Olenellus 

 zone. In this memoir Mr. Marcou gives the History— 1837-1881— of the Taconic sys- 

 tem and valuable letters of Dr. E. Emmons, Joachim Barrande and E. Billings, ad- 

 dressed to him, from 1860 to 1882, on that question. 



1886 (Dec). Mr. "Walcott published his "Second contribution to the studies of the 

 Cambrian faunas of North America (Bulletin U. S. Geol. Survey, No. 30, Washington), 

 containing at pp. 15, 16, and 17, a Georgia section, taken on almost the same line as the 

 one given by Mr. Marcou in 1880. He calls the strata " Middle Cambrian = Georgia for- 

 mation or Olenellus," with a thickness of 4500 feet. The Georgia slates, No. 6 of the 

 section, 200 feet, contains, besides the fossils already described, several new species, 

 Climacograptus? Emmonsi, Orthisina transversa and Microdiscus Parheri; and also 

 several found before in other places, but not in this locality, before Mr.Walcott's researches 

 at the Parker's quai-ry. 



" The Georgia section is the most complete yet taken in Vermont," says Mr. Walcott, 

 showing that Mr. Marcou's researches limited between Georgia, Phillipsburgh and 

 Chazy, are amply justified as the most important region of the Taconic, north of the 

 Taconic range. In beginning his studies of the Taconic system, at the same spot, 

 twenty-foiu- years after him, Mr. Walcott had a base, on which he was able to improve 

 and correct errors, at the same time that he brought with him his experience and knowl- 

 edge of the Taconic system of Nevada and the Great Canon of the Colorado. 



Paleontological remarls.— The paleontological part of Mr. Walcott's memoir under 

 the title of, : Description of the Middle Cambrian fauna, pp. 72-222, is excellent and 

 of great value to the progress of the Taconic question. Apart from a few discrepan- 

 cies in the synonymy of species, and priority of publications, both easy to con-ect, I shall 

 call attention only to a few points. 



