442 THE CANADIAN NATURALIST. [Vol. vi. 



merate which holds in its pebbles the organic remains of the 

 underlyiog strata of the second fauna. 



To the north-eastward, the island of Anticosti in the gulf of 

 St. Lawrence, presents a succession of about 1400 feet of calcar- 

 eous strata rich in organic remains, which, according to Mr. 

 Billings, include the species of the Medina, Clinton and Niagara 

 formations, and were named by him, in 1857, the Anticosti 

 group. They rest upon nearly 1000 feet of almost horizontal 

 strata, consisting of limestones and shales rich in organic remains, 

 with many included beds of limestone-conglomerate. This series 

 has by the Geological Survey of Canada been referred to the 

 Hudson-River group, but notwithstanding the large number of 

 forms of the second fauna which it contains. Prof. Shaler is dis- 

 posed to look upon it as younger, and belonging rather to the 

 succeeding division. There seems not to have been any marked 

 paleontological break between the second and third faunas in 

 this region ; and it is worthy of note, in this connection, that in 

 the outlying basin of paleozoic rocks, found at Lake St. John, to 

 the north of Anticosti, Halysites catenulatus is met with in 

 limestones associated with many species of organic remains char- 

 acteristic of the Trenton and referred to that group. [Geology 

 of Canada, page 165.] 



The strata to which, in 1857, Mr. Billings gave the name of 

 the Anticosti group were at the same time designated by him 

 Middle Silurian, in which he subsequently included the local 

 sub-division known as the Guelph formation, which in westera 

 Ontario succeeds the Niagara; the name of Upper Silurian 

 being thus reserved for the Lower Helderberg division and the 

 underlying Onondaga formation [Report Geol. Sur, Can. 1857, 

 page 248, and Geol. Can. page 20.] Both the Guelph and the 

 Onondaga have been omitted from the table on page 312; the 

 Guelph because it was not recognized in the New York system, 

 and is by some regarded as but a sub-division of the Niagara ; 

 and the Onondaga, for the reason that it is a local deposit of 

 magnesian limestones, wiih gypsums and rock-salt, destitute of 

 organic remains. 



As to the name of Middle Silurian, it had some years pre- 

 viously been used by the officers of the government Geological 

 Survey in Great Britain to designate the Lower and Upper 

 Llandovery rocks; but is referred to in 1854 by Sedgwick as one 

 that had, at that time, already been abandoned, (L. E. & D. 



