86 Horner's Geological Address. 



be compared, in addition to what we already have of many 

 of the palaeozoic and secondary formations. 



A paper by Captain Bayfield read before us last April, and 

 published in November in our Journal, gives us much im- 

 portant information on the Silurian rocks that prevail to a 

 great extent in Canada ; and we are indebted for a more 

 accurate knowledge of the same class of rocks in the Isle of 

 Man to the Rev. J. Cumming, in the first part of a descrip- 

 tion of that island, read last June. 



We learn from the " Geology of Russia," that both in that 

 country and in Scandinavia, a series of ancient deposits 

 cover a great tract of country, which, in all their great fea- 

 tures, and often in their minute characters, are identical with 

 the Silurian series of the British Isles, and that they are 

 equally divisible into two distinct groups, and are also over- 

 laid by a true Devonian formation. In the central and 

 southern parts of the continent of Sweden, the lower Silurian 

 rocks only occur, but the adjoining islands of Oesel, Dago, 

 and Gothland are mainly composed of Upper Silurian rocks, 

 affording better types than Wenlock or Dudley. Describing 

 the rocks near Katchkanar, on the eastern flank of the Urals, 

 Sir R. Murchison says, " The banks of the river Is are com- 

 posed for a considerable distance of white limestone, thickly 

 tenanted by large Pentameri, some Trilobites, and shells 

 which we hailed as true Silurians, and worthy of the very 

 region of Caractacus. We were enchanted when we disco- 

 vered myriads of them undistinguishable from the Pentame- 

 rus Knightii ; so that, seated on the grassy banks of the Is, 

 we might for a moment have fancied ourselves in the mea- 

 dows of the Lug at Aymestry.'' Of the Lower Silurian fos- 

 sils of Russia a few only are absolutely identical with forms 

 of the same age in the British Isles ; but the mass of them 

 is essentially the same as that of the mainland of Scandi- 

 navia ; which region being intermediate between England 

 and Russia, is found to contain a considerable number of 

 forms common to deposits occupying the same position in 

 both the other countries. In the lowest part of the Lower 

 Silurian rocks that skirt the southern shores of the Baltic, a 

 grit occurs so abounding in a minute shell, the Ungulite or 



