472 Notices of Memoirs — Dr. T. Sternj Sunt. 



visionally as distinct from the Cambrian. It has yielded in Ontario, 

 besides ScoUthiis, the Eozoon Canadense, and may, perhaps, be 

 regarded as the connecting link between the Eozoic and Palssozoic 

 ages. 



The Upper Taconic, or so-called Quebec group, in Eastern North 

 America, is separated by a stratigraphical break from the succeeding 

 portion of the Cambrian, the Bala group (Trenton, Utica, and 

 Lorraine) ; while, on the contrary, the supposed discordance in the 

 regions just mentioned at the summit of the latter, corresponding to 

 the division between Cambrian and Silurian in Wales, appears to 

 have been based on a misconception. There is, however, an 

 important palasontological break at this horizon connected with a 

 great deposit of barren detrital rocks, which marked the close of the 

 Cambrian period, and the aiithor records his opinion that the name 

 of Lower Silurian, as well as that of Siluro-Cambrian, which he, 

 with others, has applied to the Bala or upper division of the Cambrian, 

 is to be rejected as being historically incorrect, and as tending to 

 perpetuate false views of the palseontological relations between these 

 and the succeeding rocks. The early advocates in North America of 

 the notion of the metamorphism of Palaeozoic rocks taught, in the 

 first place, the stratigraphical equivalence of the Taconic, or L. and 

 M. Cambrian, with the U. Cambrian, and further maintained that 

 these rocks had suffered various degrees and kinds of metamor- 

 phism, as the result of which they had assumed, in different areas, 

 the characters of the Taconian, Montalban, Huronian, and Lauren- 

 tian ; the lithological differences between these several series being 

 regarded as marks of the greater or less alteration which it was sup- 

 posed these uncrystalline Cambrian sediments had undergone. Other 

 geologists have imagined portions of these same crystalline formations 

 in North America to be altered strata of Silurian, Devonian, and 

 even of Triassic age. The great groups of Eozoic rocks already 

 described constitute, however, in the author's opinion, as many great 

 stratified series, which, before the Cambrian time, existed in their 

 present crystalline condition, and had been successively subjected to 

 the accidents of uplift, contortion, and denudation, so that the newer 

 Eozoic groups were, at the beginning of the Palaeozoic period, distri- 

 buted irregularly over the floor of fundamental Laurentian gneiss. 

 These various crystalline groups are found, with a singular persistence 

 and uniformity of ethnological character, from Alabama to Newfound- 

 land, along the Atlantic belt, and thence westward through Canada, 

 to the great lakes, and beyond, in the vast region of the Cordilleras 

 to the Pacific slope. The author had some years since pointed out 

 the remarkable similarity between the various crystalline groups of 

 North America and the crystalline I'ocks of the British Islands, and 

 had lately been able, by new observations, to confirm his conclusions. 

 Among the crystalline formations of Donegal he had indicated repre- 

 sentatives of Laurentian, Montalban, and Huronian, and the latter he 

 had recently observed largely developed in Argyleshire and Perth- 

 shire. To the Huronian, also, he refers the green schists of Anglesea 

 and Carnarvonshire, in both of which regions the orthofelsite, or 



