322 CD. Walcott — The Taconic System of Emmons. 



conic " cany characteristic Lower Silurian (Ordovician) fossils, 

 as, also, do the shales overlying the limestones. 



In 1859 (Manual of Geology, p. 87), Br. Emmons for the 

 first time compared his jElliptocephala asaphoides with the 

 genus Paradoxides, of Barrande's Primordial Zone, stating 

 that the Taconic Paradoxides is also Silurian, and hence it is 

 shown that the Primordial Zone, in Bohemia, is in coordina- 

 tion with the upper series of Taconic rocks. This statement 

 is the first known to me upon which, either by paleontologic 

 or stratigraphic evidence, Dr. Emmons could base his assertion 

 that any portion of the " Taconic System " was of pre-Pots- 

 dam age. 



The want of clearness in his views is well shown by the 

 extract already quoted from his letter of Nov. 20, 1860, pub- 

 lished by Prof. Marcpu. " His [Barrande's] Primordial group 

 is only Lower Silurian. I conceive we have exactly his 

 Primordial group in the band of slates containing the Para- 

 doxides." — What becomes of the stratigraphic break between 

 the Lower Silurian and Taconic rocks if the " Black slates " 

 are still retained in the " Taconic System," remains unex- 

 plained. If removed the fossils go into the Lower Silurian 

 with it. 



Dr. Emmons described several species of graptolites* from 

 the " Taconic System," the majority of which are now known 

 to also occur in the Hudson Terrane, in the valley of the 

 Hudson. On the map, I have given the distribution of the 

 Hudson Terrane in the Taconic area, as determined by strati- 

 graphic and paleontologic evidence. It is in the central belt, 

 carrying the red slates, that the graptolites occur which led 

 Dr. Emmons to include, as a matter of necessity, if he put 

 the red slates in the Taconic, the dark, argillaceous shales of 

 Hudson Terrane at Troy, Albany, and Baker's Falls, in the 

 Hudson Valley, for they contain the "beautiful graptolites "f 

 referred to by him in I860. At Albany, N. Y., however, the 

 graptolite beds contain a characteristic Trenton-Hudson fauna4 

 This removes a considerable portion of the " Upper Taconic " 

 strata from the " Taconic System." 



* Am. Geol., vol. i, pt. 2, pp. 104-111, 1856. 



f See letter to Prof. Jules Marcou ; Proc. Am. Acad. Arts and Sci., vol. xii, p. 

 188, 1885. 



X Mr. C. E. Beecher found three of the same species of graptolites (Climaco- 

 graptus Mcornis, Dicranograptus ramosus and Diplograptus mucronatus) as those 

 found by me in the "Taconic Slates" of Washington and Rensselaer counties, 

 associated with Brachiopoda, 5 species ; Lamellibranchiata, 16 species; Ptero- 

 poda, 2 species ; Gasteropoda, 3 species ; Cephalopoda, 2 species ; Annelid, 1 spe- 

 cies ; Crustacea, 1 species, and Trilobita, 2 species. For names of species, see 

 Mr. Beecher's paper. (Thirty-sixth Ann. Rep. N. T. State, Mus. Nat. Hist., p. 

 ?8, 1884). 



