564 Pi'of. T. Sterry Hunt — On Cambrian and Silurian. 



Lower Potsdam of Mr. Billings. Future discoveries may perhaps assign it a place 

 below instead of above the Menevian horizon. 



The characteristic Menevian fauna in and near St. John, New Brunswick, is 

 found in a band of about 150 feet, towards the base of a series of nearly vertical 

 sandstones 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 2000 feet, contains Lingtila throughout, but 

 has yielded no remains of a higher fauna. The same Menevian forms have been 

 found in small outlying areas of similar rocks, at two or three places north of the 

 St. John basin, but to the south of the New Brunswick coal-field. To the north 

 of this is a broad belt of similar argillites and sandstones, which extends south- 

 westward into the State of Maine. This belt has hitherto yielded no organic remains, 

 but is compared by Mr. Matthew to the Cambrian rocks of the St. John basin, and 

 to the gold-bearing series of Nova Scotia (Geol. Journ. vol. xxi. p. 427), which 

 at the same time resembles closely the Cambrian rocks of south-eastern Newfound- 

 land. This was remarked by Dr. Dawson in i860, when he expressed the opinion 

 that the auriferous rocks of Nova Scotia were " the contmuation of the older slate 

 series of Mr. Jukes in Newfoundland, which has afforded Faradoxides" and pro- 

 bably the equivalent of the Lingula-flags of Wales. (Supplement to Acadian 

 Geology (i860), page 53; also Acad. Geol. 2nd ed. p. 613.) Associated with 

 these gold-bearing strata, along the Atlantic coast of Nova Scotia, occur fine- 

 grained g'neisses, and mica-schists with andalusite and staurolite ; besides other 

 crystalline schists, which are chloritic and dioritic, and contain crystallized epidote, 

 magnetite and menaccanite. These two types of crystalline schists (which, from 

 their stratigraphical relations, as well as from their mineral condition, appear to 

 be more ancient than the uncrystalline gold-bearing strata) were in i860, as now, 

 regarded by me as the equivalents respectively of the White Mountain and Green 

 Mountain series of the Appalachians ; as will be seen by reference to Dr. Dawson's 

 work just quoted. At that time, however, and for many years after, I held, in 

 common with most American geologists, the opinion that these two groups of 

 crystalline schists were altered rocks of a more recent idate than that assigned to 

 the auriferous series of Nova Scotia by Dr. Dawson ; who was much perplexed by 

 the difficulty of reconciling this view with his own. The difficulty is however at 

 once removed when we admit, as I have maintained for the last two years, that 

 both of these groups are pre-Cambrian in age. (Amer. Jour. Sci. ii. 1. 83 ; address 

 to the Amer. Asso. Adv. Sci. August, 1871.) 



A notice by Mr. Selwyn. of some of these crystalline schists in Nova Scotia will 

 be found in the report of the Geological Survey of Canada for 1870. He there 

 remarks, moreover, the close lithological resemblances of the gold-bearing strata 

 to the Harlech grits and Lingula-flags of North Wales, and announces the dis- 

 covery among these strata of peculiar organic markings regarded by Mr. Billings 

 as identical with the Eophyton Linrmanum, which is found at the base of the 

 Cambrian in Sweden. 



[The palseontological features of the rocks are then referred to more particularly, 

 and the marked break that occurs between the Levis and Trenton faunas.] 



The history of the introduction of the names of Silurian and Devonian into 

 North American geology demands our notice. Prof. Hall, while recognizing in 

 the rocks of the New York system the representatives alike of the British 

 Cambrian, Silurian and Devonian, wisely refrained from adopting this nomen- 

 clature, drawn from a region where wide diversities of opinion and controversies 

 existed as to the value and significance of these divisions. Lyell, however, in the 

 account of his first journey to the United States, published in 1845, applied the 

 terms Lower and Upper Silurian and Devonian to our Palaeozoic rocks. Later, in 

 1846, de Verneuil, the friend and colleague of Murchison in his Russian researches, 

 visited the United States, and on his return to France published, in 1847,' an elaborate 

 comparison between the European Palaeozoic deposits and those of North America, 

 as made known by Hall and others. He proposed to group the whole of the rocks 

 of the New York system, up to the summit of the Hudson- River group, in the 

 Lower Silurian, and the succeeding members, including the Lower Helderberg, 

 and the overlying Oriskany, in the Upper Silurian ; the remaining formations to 

 the base of the Carboniferous system being called Devonian. 

 » Bull. Soc. Geol. de Fr. II. iv. p. 646. 



