160 THE CANADIAN NATURALIST. [Yol. vil. 



BREAKS IN THE AMERICAN PALEOZOIC SERIES. 



By Prof. T. Sterry Huxt. 



The author began by considerations on the value and signifi- 

 •cance of breaks in the succession of strata and of organic re- 

 mains ; he then referred to the classification of the palaeozoic 

 rocks of the New York series, and showed that Hall in 1842, 

 and again in 1847, pointed out the existence therein of a fauna 

 older than what was then called Silurian by Murchison, or was 

 .known in Great Britain, maintaining that our comparison with 

 British rocks must commence with the Trenton limestone, the 

 equivalent of the Llandeilo or Upper Cambrian of Sedgwick 

 ('(Lower Silurian of Murchison). The rocks below this horizon 

 in America were the equivalent of the Lower Cambrian of Sedg- 

 wick, which, when they were found to be fossiliferous were 

 •wrongly claimed by Murchison as part of the Silurian. He 

 sketched the history of the introduction of the nomenclature of 

 Murchison into our American geology, and then proceeded to 

 show the existence of a break both stratigraphical and palaeon- 

 tolo2;ical at the base of the Trenton. The contact between the 

 ■calciferous siindrock and the unconformably overlying Trenton 

 is seen in Herkimer County, N.Y,, according to Hall, The so- 

 iCalled fossiliferous Quebec group of Logan, the primal and 

 auroral of Rogers, which extends along the great Appalachian 

 valley from the Lower St. Lawrence to Georgia, corresponds to 

 the Lower Cambrian, and the Potsdam Calciferous and Chazy 

 formations are its equivalents in the valley of the Ottawa and 

 Lake Champlain much reduced in thickness. These are over- 

 laid by the rocks of the Trenton and Hudson River groups 

 (Upper Cambrian) which in various localities to the north over- 

 lap the older fossiliferous rocks, and repose on the crystalline rocks, 

 indicating a considerable continental movement corresponding to 

 the break in palaeontological succession. The relation between 

 these is explained by Logan as resulting from a movement pos- 

 terior to the deposition of the Hudson River group, which pro- 

 duced a great uplift of several thousand feet, extending for more 

 than 1,000 miles. While showinsr that there have been move- 

 ments in parts of the region since that period, the author rejects 

 the explanation, and shows that the relation between the two is 

 due to the fact that the Trenton and the Hudson River rocks 



