90 Horner's Geological Address. 



not too highly praise the patience and perseverance of Sir 

 R. Murchison and his fellow-travellers. 



Although recognised by a remarkable degree of identity 

 in fossil contents, and especially in regard to ichthyolites, as 

 a deposit of the same age as the old red sandstone in our own 

 country, it is lithologically very different in most places. 

 Sometimes it is made up of numerous alternations of flat- 

 bedded, light yellowish limestones, often so impregnated with 

 magnesia as to be scarcely distinguishable from some of the 

 magnesian limestones of England, or the Zechstein of Thu- 

 ringia ; at other times it is composed of red and green flags 

 and marls ; and, on the flanks of the Urals, this series is re- 

 presented by black and calcareous slaty masses. Moreover^ 

 it is comparatively rare as a red sandstone. But the fishes 

 and shells the beds contain soon rectify the mistake as to 

 the true position of these rocks, into which their mineral as- 

 pect alone might lead the most experienced geologist, should 

 he not have an opportunity of seeing them reposing on true 

 Silurian rocks, and covered by carboniferous strata. In re- 

 gard to the evidence from fossil contents, it is so complete in 

 these Russian deposits as not only to establish their own 

 position, but to corroborate the soundness of the reasoning 

 which unites the old red sandstone of Scotland with the slaty 

 limestones and schists of Devonshire and the Continent ; for 

 they contain the characteristic fishes of the former, and the 

 molluscs of the latter. The examination of Russia, Sir R. 

 Murchison further observes, has afforded numberless proofs 

 that the ichthyolites and molluscs which in Western Europe 

 are separately peculiar to smaller detached basins, were there 

 inhabitants of many parts of the same great sea. Of the 

 known Russian ichthyolites, two-thirds are specifically the 

 same as those of the same epoch in Great Britain. 



The neighbourhood of Dorpat in Lithuania is a very re- 

 markable locality for the ichthyolites of this age ; they are 

 there met with of so gigantic a size, that they were supposed 

 to belong to Saurians, until the closer examinations of Pro- 

 fessor Asmus of Dorpat, M. Agassiz, and Professor Owen, 

 disclosed their true nature. A note by Professor Owen, in 

 the Appendix to the ** Geology of Russia," is highly instruc- 



