XV.] CAMBRIAN ANI> SILURIAN IN NORTH AMERICA. 417 



Professor Shaler is disposed 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 palaeozoic 

 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 which are characteristic 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 subdivision known as the Guelph formation, which in 

 western 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 386 : 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 or Salina, for the 

 reason that it is a local deposit of magnesian limestones, with 

 gypsums and rock-salt, destitute of organic remains. 



[The name of Middle Silurian was at one time used by the 

 geological survey of Great Britain to designate the Lower and 

 Upper Llandovery rocks, but was not employed by Murchison 

 either in his Silurian System or in the various editions of 

 Siluria. It is rejected by Lyell (Students' Manual of Geology, 

 page 452), and was referred to in 1854 by Sedgwick as a term 

 then already abandoned. (London, Edinburgh, and Dublin 

 Philosophical Magazine (3), VIII. 303, 367, 501.) Piamsay, 

 moreover, though he speaks of the rocks as an intermediate 

 series, does not make use of the term Middle Silurian. (Memoirs 

 Geological Survey, III. Part II. page 2.) It is, however, once 

 more applied by Hicks in 1873, and made to embrace, as 

 before, the Lower Llandovery, included by Sedgwick in his 

 18* AA 



