426 J. D. Dana — Brief history of Taconic ideas, 



Stockbridge (Eolian) limestone Trenton fossils within half a 

 mile of the Massachusetts line in Pownal ; other Lower Silu- 

 rian fossils on both sides of Mt. Anthony, three miles s6uth of 

 Bennington, a Trenton crinoid included ; Trenton fossils in 

 Williamstown, at the Hopper, at the west foot of Greylock and 

 others in Berlin south of South Berlin ; and at Hoosic Falls 

 in Rensselaer Co., New York, west of Bennington, Trenton 

 fossils again.* — The results warrant full confidence, he says, in 

 the Calcifeious-Trenton age of the limestone. Further, in the 

 slates at Hoosic he obtained Graptolites, as had long before 

 been found, of Hudson age. In the study of the quartzyte of 

 Vermont, specimens in the Amherst cabinet (Amherst, Mass.) 

 afforded him the species N'othozoe Vermontana, Olenellus 

 Thompsoni and Hyolithes communis / the quartzyte mountain, 

 two miles east of Benningtoo, Vt., gave him specimens of 

 Nothozoe, Olenellus and Hyolithes, and the quartzyte of the 

 west summit of Clarksburg Mountain or Oak Hill, on the 

 borders of Williamstown, an Olenellus. These discoveries 

 were preceded in 1886 by finding, along with Professor Dwight, 

 Hyolithellus micans in the limestone resting on the quartzyte 

 of Stissing Mountain in Dutchess Co., N. Y. (the quartzyte 

 referred to by Professor Emmons), and heads of Olenellus 

 Thomjisoni at the same place in the quartzyte itself. 



The colored map accompanying his paper in volume xxxv 

 (1888) of this Journal has the above mentioned localities of 

 fossils indicated, and also those of Cambrian age within the 

 area of the Taconic slates over eastern New York and the 

 borders of Yermont. The fossils are positive evidence of the 

 age of the slates at the localities where they occur. But how 

 far the slates away from the localities are Cambrian, or how 

 far they are, instead, of the Hudson group, with faults here 

 and there bringing up Cambrian, in Eastern New York, as in 

 Dutchess County, remains yet to be ascertained. The doubt 

 does not affect the general conclusion from the facts. Further, 

 Mr. Walcott made out that the quartzyte formation, and the 

 Bald Mountain and Georgia slates were alike in belonging dis- 

 tinctively to the Olenellus section of the Cambrian. 



These discoveries of Mr. Walcott afford the first demonstra- 

 tion of the age of the quartzyte, and give new precision to 

 our knowledge of the age of the Georgia, Bald Mountain and 

 associated slates. Besides this, they give full completeness to 

 the proof, that had been for years accumulating, of the Lower 

 Silurian age of the Taconic limestone. They show, moreover, 

 that the Primordial beds constituting Emmons's "Upper" 

 Taconic, on account of which the terms Primordial and Ta- 

 conic have by some been thought to be rightful synonyms, are 



* C. D. Walcott, this Journal, III, xxxiv, 187. 1887, xxxv, 229, 307, 394, 1888. 



