XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA. 407 



group, the fossiliferous strata of St. John, New Brunswick, 

 being referred to the same horizon ; which corresponds to the 

 Menevian of Wales, now recognized as the summit of the Lower 

 Cambrian. The succession of the rocks containing these two 

 faunas in southeastern Newfoundland is not yet clear ; the 

 Lower Potsdam fauna is regarded by Mr. Billings as identical 

 with that found on the Strait of Bellisle, at Bic (on the south 

 shore of the river St. Lawrence, below Quebec), at Georgia in 

 Vermont, and at Troy, New York j but in none of these other 

 localities is it as yet known to be accompanied by a Menevian 

 fauna. The trilobites hitherto described from these rocks 

 belong to the genera Olenellus, Conocoryphe, and Agnostus ; 

 neither Paradoxides, which characterizes the Menevian and the 

 underlying Harlech beds in Wales, nor Olenus, which there 

 abounds in the rocks immediately above this horizon, having 

 as yet been described as occurring in the Lower Potsdam of 

 Mr. Billings. Future discoveries may perhaps assign it a place 

 below instead of above the Menevian horizon. 



[To the above genera of trilobites occurring at Troy, Mr. 

 Ford has since (in 1873) added Microdiscus, which has also 

 been found at Bic. This genus is common to the Menevian 

 and the underlying Harlech rocks in Wales, and is also, accord- 

 ing to Emmons, found with graptolites in Augusta County, 

 Virginia. The strata which contain this fauna at Troy, as 

 described by Ford, are of considerable thickness, consisting 

 of limestones with coarse sandstones and shales, which, as the 

 result of a dislocation or of an overturned and eroded anticlinal, 

 are made to overlie, in apparent conformity, the beds of the 

 Utica or Hudson Eiver group, the whole dipping eastward. 

 (American Journal of Science (3), VI. 134.)] 



The characteristic Menevian fauna in and near St. John, 

 New Brunswick, is found in a band of about one hundred and 

 fifty feet, towards the base of a series of nearly vertical sand- 

 stones and argillites, underlaid by conglomerates, and resting 

 upon crystalline schists, in a narrow basin. The series, the 

 total thickness of which is estimated by Messrs. Matthew and 

 Bailey at over 2,000 feet, contains Lingula throughout, but has 



