B)'. T. 8terry Runt — The Eozoio Rocks of N. America. 509 



Haronian, and the Montalban. There are found in the quartzites 

 of this series the impressions of Scolithus, and in the limestone other 

 undetermined forms. This is the Lower Taconio series of the late 

 Dr. Emmons, wliich we distinguish by the name of Taconian. 

 Some late writers have by mistake confounded it with the Upper 

 Taconio of the same author, a distinct group, which Emmons 

 declared to be the equivalent of the primoi'dial (Cambrian) of 

 Barrande. The Taconian is widely spread in eastern North America, 

 and appears to be also represented around Lake Superior by what 

 has been called the Animikie series. There is reason to believe 

 that on account of certain lithological resemblances between the 

 Taconian and the Huronian, the two have been in some localities 

 confounded, and that portions which have been called Huronian are 

 really Taconian. The latter the writer has elsewhere compared 

 with a great series of similar schists and quartzites, including 

 serpentine, anhydrite, dolomite, and marbles, greatly developed in 

 northern Italy, where it overlies the younger gneissic and mica- 

 schist series, and has been by various observers successively referred 

 to the Mesozoic, the Palaeozoic, and the Eozoic periods. 



It now remains to say something upon the relations of these 

 different crystalline Eozoic series to the Cambrian which succeeds 

 them. Forty years since there were two schools among American 

 geologists. One of these schools admitted the existence between the 

 ancient gneissoid rocks (subsequently named Laurentian and Norian) 

 and the fossiliferous limestones of the second fauna (Ordovician) of 

 nothing more than the Cambrian subdivisions known as the Potsdam 

 sandstone and the Calciferous sand rock, which in the vicinity of the 

 Adirondack Mountains separate these ancient crystalline rocks from 

 the Ordovician strata. 



The other school of stratigraphists recognized the existence, in 

 this interval, in the region to the east of Lake Charaplain, of several 

 series of crystalline rocks, including what we have already described 

 imder the names of Arvonian, Huronian, Montalban and Taconian, 

 besides a younger series of uncrystalline sediments of great thick- 

 ness, designated by Eaton the First as Transition Greywacke. This 

 was by him declared to be separated by the limestones of the second 

 fauna from the Secondary Greywacke, a series closely resembling 

 the Transition Greywacke. The first-mentioned school denied the 

 existence of the Transition Greywacke, and maintained that the 

 group thus designated was identical with the secondary Greywacke. 

 The geologists of this school further supposed that all the different 

 series of crystalline rocks just named were nothing more than the 

 same Secondary Grej'wacke, with the addition of the underlying 

 fossilifei'ous limestones, in a state of alteration more or less profound ; 

 the series in different areas assuming successively the character of 

 Taconian, Montalban, Huronian, and even, as some imagined, of 

 Laurentian. The recent progress of American stratigraphy has fully 

 justified the views of the second named and older school of Eaton. 

 It has been shown that the First or Ti'ansition Greywacke of this 

 author, which was the Upper Taconic of Emmons, and includes the 

 Primordial or Cambrian fauna, rests in unconformable stratification 



