166 PROCEEBINGS OF THE GEOLOGICAL SOCIETY. 



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 lime- 

 stones, often so impregnated with magnesia as to be scarcely distin- 

 guishable from some of the magnesian limestones of England, or the 

 Zechstein of Thuringia ; at other times it is composed of red and 

 green flags and marls ; and, on the flanks of the Urals, this series is 

 represented 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 aspect alone might lead the 

 most experienced geologist, should he not have an opportunity of 

 seeing them reposing on true Silurian rocks and covered by car- 

 boniferous strata. In regard 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 reason- 

 ing 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 mollusks of 

 the latter. The examination of Russia, Sir R. Murchison further 

 observes, has afforded numberless proofs that the ichthyolites and 

 mollusks 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 spe- 

 cifically the same as those of the same epoch in Great Britain. 



The neighbourhood of Dorpat in Lithuania is a very remarkable 

 locality ibr 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 Professor 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 instructive, as showing the great importance of an examina- 

 tion of the internal structure of the substance of fossil teeth by the 

 microscope, in determining the classes of animals to which they 

 have belonged. He points out, by a striking illustration, how the 

 microscopic labours of the philosopher in his closet may have the 

 most important eff'ect on questions that appear to be far remote 

 from the subject of his inquiry. Had the teeth under consideration 

 continued to be held to belong to Saurians, the matrix in which 

 they are imbedded having a close resemblance in mineral character 

 to magnesian limestone, or to members of the new red sandstone 

 series, borings for coal might have been carried on in many parts of 

 Russia, involving vast losses ; but the teeth having been proved to 

 belong to a class of fishes that are characteristic of the old red 

 sandstone, all expectations of finding profitable seams of coal are 

 known to be vain. 



If we now cross the Atlantic with Mr. Lyell, and visit the Silu- 

 rian region of North America, we find that series of rocks covered 

 by others having characters corresponding with those of the Devo- 

 nian group in Europe. The rocks of the Appalachian chain con- 



