79 



these is that in which Divisions 3 and 4 of the Anticosti rocks are situ- 

 ated, which, as above stated, may be recognized in the Llandovery series, 

 and is also, most certainly, the Clinton of Canada West and New York. 

 The other is the Lower Liugula Flags, to be noticed further on. 



In Canada West and New York there is an almost total palneontological 

 break between the Clinton and Hudson River, partly filled by the nearly 

 unfossiliferous Medina Sandstone. In Anticosti, Divisions 1, 2, and 3 

 seem to occupy the jDlace of this break, and in England, apparently the 

 Lower Llandovery, and, perhaps, some part of the Caradoc (including the 

 breaks mentioned by Professor Ramsay.) 



From the top of the Hudson River down to the base of the Black River 

 limestone, there is no break, but all is occupied by a single, immense, 

 highly characteristic, and compact fauna. The lower, middle, and upper 

 portions of this series may be easily recognized by species peculiar to each, 

 but the abundant and dominant forms, those that give a facies to the whole, 

 are found throughout. 



Between the Black River and Chazy there is another gap, but it is 

 not of so decided a character. These two formations are connected by 

 about twenty species. At the base of the Chazy in Canada West and New 

 Yoi'k, there occurs a great break, the importance of which has only be- 

 come apparent during the last six years. The Lower Silurian of America 

 can be divided into two principal groups — one above the break at the base 

 of the Chazy, and the other below. The former includes the Chazy, 

 Black River, Birdseye, Trenton, Utica, and Hudson River formations. 

 The lower comprizes a series of formations, which are only now beginning 

 to become known. These I shall more specially notice, commencing with 

 the lowest. 



The St. John's group, near the city of St. John, in New Brunswick, 

 has lately been well characterized by Messrs. Matthew, Hartt, and Bailey. 

 It consists of about 3000 feet of black slates and sandstones, and is under- 

 laid conformably by a series of rocks very like those of the Cambrian. 

 The fossils were determined by Mr. Hartt, several years ago, to be all 

 primordial, and he correctly placed the formation in the horizon of Barande's 

 "Etage C." We have lately, through the kindness of Mr. G. F. 

 Matthew, received a collection for comparison. Among them I find the 

 plates of a Cystidean, OrtUsI 1 sps,, another brachiopod, hke sl Disci7ia, 

 and species of the genera Faradoxides, Oonocephalites, Arionellus, 

 Microdisciis, and Agnostus, with some others, all so closely allied to those, 

 so excellently described and figured by Salter in his various papers, that 

 I have no hesitation whatever in pronouncing these rocks to be the Lower 

 Lingula Flags. I think this horizon is now as certainly determined in 

 America by these fossils as is that of the Llandovery by the fossils of 

 Divisions 3 and 4 of the Anticosti group. The St. John's slate (Jukes) 



