AND THE EEPORT ON THE GEOLOGY OF VERMONT. 129 



the oldest palaeozoic rocks, had made a new genus from a specimen of a Trlnucleus : 

 a genus which, after all, is regarded by Messrs. Salter and Walcott as being a good one 

 when applied to four other fossils, all of the American primordial fauna. 



OraptoUtas zones of America. — Fiually, Mi'. Walcott, at p. 92, makes strictures on an 

 extract of a letter of Emmons to Marcou, published in " Taconic system, etc." {Proceed. 

 Amer. Acad., Vol. xii, p. 188, CamJjridge, 1885), in i-egard to the beautiful Taconic 

 Graptolites referi'cd by Mr. James Hall to the Lori'aine shales (Hudson River gronjj). 

 Professor Walcott thinks that " Emmons had not a ck^ar idea of the position of the 

 shales of the Hudson valley that contains the OraptoUtes . . . nor of the shales at 

 Pointe-Levis carrying the graptolitic fauna." Farther on, he adds, " Pi'ofessor Marcou 

 refers the strata containing the Clraptolitcs to the Taconic, and places it below the Pots- 

 dam sandstone, but I think without either stratigraphic or palaeontologic evidence." 

 Mr. Marcou has given proofs of the Taconic age of the ^' Black slates " of Emmons at 

 Swanton, Highgate, Phillipsburgh and Quebec, in publishing geological maps, sections 

 and tabular views, repeatedly from 1861 to 1885. 



The graptolitic questiou must be studied not in doors, but in the field, and all that I 

 have seen in Vermont and at Quebec confirms and sustains the opinion expressed by 

 Dr. Ennnons. 



The Director of the Canada Geological Survey, Mr. Selwyn, says: "Unfortunately in 

 Canada geology, hitherto the stratigraphy has been made subordinate to mineralogy 

 and palaeontology" (see The strati r/rajjJiy of the Quehec group and the older criistalline 

 rocTxS of Canada, p. 14, 1879, Monti-eal), a remark, l)v the Avay, of wliich he made no use 

 himself, and which is equally true for the whole Taconic area in the United States. 



It is to be hoped that the paleontologists, who occupy themselves more especially 

 with the studies of Graptolites, will conform to stratigraphy and not force the different 

 zones of Graptolites all ovei- the world, in America as well as in Europe, Asia and Aus- 

 tralia, into the same horizon whether they belong there or not. 



There are three zones of Graptolites in the Taconic system of eastern America. The 

 oldest is in the St. John group and Georgia slates. The second horizon exists in the 

 Pointe Levis or Pliillipsburgh group, where are the celebrated com])ound Graptolites, 

 with many others. Then the third zone in the Swanton slates, near Swanton's bridge, 

 and in the Quebec citadel slates at Quebec city and at the island of Orleans. Finally \n 

 the Utica and Loi-raine shales, there is anothei" graptolitic zone represented by only fonr 

 or six species at most. 



I do not enter into subdivisions of those four different great graptolitic zones, which 

 according to localities can be divided in stages and even in beds; for only local descrip- 

 tions and minute surveys can give tlwjse limited zonal details. But I give two tabular 

 views which show at a glance the great divergence of opinions existing in regard to 

 classifications and nomenclature. 



Table A is taken from "C. Lapworth on Graptolites from Lower Palaeozoic rocks" 

 (Trans. Roy. Soc. Canada, 4°, 1886, p. 183, Montreal). 



I have reduced it to a smaller form, suppressing the names of the species of Graptolites 

 and several names of localities in Canada and jSTew York, l)ut keeping carefuU}^ the divi- 

 sions and classifications of Professor Lapworth. 



MEMOIRS BOSTON SOC. NAT. HIST., VOL. IV. 19 



