294 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



a strong band of Lower Silurian limestone*, in which Mr. Peach has 

 found weU-defined animal forms belonging else only to the Lower 

 Silurian stage of Canada. They consist of an Oncoceras, an Orthoceras, 

 the Maclurea Peachii, and Ophileta com/pacta, — the last two genera 

 being most remarkable in themselves and in their being thus found 

 twice grouped together. "We have here, therefore, an argument 

 of some force in favour of our supposition, but which would have 

 been very strong had these fossils of the East and the West been 

 specifically the same, which they are not. To these facts we may 

 add the long- ascertained relationship between the Irish and New 

 York fossils, according to Portlock. 



The greater part of the Carboniferous plants of Pennsylvania and 

 Nova Scotia are identical with European forms ; and most of the 

 remainder are closely allied to the latter. Mr. Bunbury says that 

 this points to a greater similarity of climate than at present obtains, 

 and to the possible connexion of the coal-formation areas of Europe 

 and America by groups of islands. 



In all times and epochs (whether palseozoic, mesozoic, or tertiary), 

 continuity of land, of sea, and sea-depth produced continuity or ex- 

 tension of life. Wherever, we proceed to say, there is discontinuity 

 or separation of land or of sea, the opposite sides of the barriers are 

 inhabited by diiferent races, except in special cases. 



We have hitherto spoken about community of faunae and florae ; 

 but now, in order to bring further into view the great importance of 

 contours (that is, of depressions and elevations), we wish to draw 

 attention to the extreme diJQferences between the Silurian basins of 

 Bohemia and Scandinavia, in their mineral and palseontological 

 characters, as aUuded to in p. 287. They all arise, in the opinions of 

 the best-informed geologists, from the former existence of intervening 

 coast-lines, or of great sea-depths, forbiddingprogressionor migration. 



These are subjects of the deepest interest, hitherto little looked 

 into. I earnestly recommend them to the best attention of the 

 young geologist. They promise splendid results — nothing less than 

 opening the great volume of historic geology, with its successive 

 territories and dynasties, each for a time a scene of activity and 

 happiness, and each full of wisdom, beauty, and grandeur. We at 

 length begin to see that we shall see. 



* Quart. Journ. Geol. Soc. vol. xiv. p. 502. 



