94 Horner's Geological Address. 



not exist even in the oldest of the fossiliferous beds ; far 

 their extraordinary abundance in the Devonian series, and 

 the distinct recognition of them in certain Silurian beds, 

 where, it is true, they are but imperfectly preserved, suffi- 

 ciently indicates, that, on its first appearance, that class of 

 animals was contemporary with the development of the types 

 of all the classes of invertebrate animals." 



Mr Lyell states, that the lowest rock in which ichthyolites 

 have been traced in America is the Clinton group, which may 

 be considered the bottom of the Upper, or top of the Lower 

 Silurian series. Ichthyolites have recently been found in the 

 Wenlock shale ; another step in descending order, and so far 

 in support of M. Agassiz's views. 



The Carboniferous Series. 



Although rocks of this age cover a great extent of country 

 in European Russia, extending over a tract equally vast in 

 horizontal extension with that occupied by the Devonian 

 series, there are few places, except in the coal-field of the 

 Donetz in the south, where the coal-seams are more than a 

 few inches in thickness ; and where they are thicker, they 

 are so poor in quality as to be rarely worth working. The 

 great coal-fields of England, France, Belgium, and America, 

 have no well-marked equivalents there, nearly the whole of 

 the coal-beds in the empire being, like those of Ireland and 

 the coal-fields on the banks of the Tweed, included in the 

 lower members of the system ; which, with the sandstones, 

 shales and marls, are the equivalents of our mountain lime- 

 stone, as is proved by the identity of a large series of fossils. 

 From a section of the works at Lissitchia-Balka, on the river 

 Donetz, we learn, that in a depth of 900 feet there are twelve 

 seams of coal, the united thickness of which amounts to thirty 

 feet ; they are associated with sandstones, grits, and shales ; 

 and eight beds of sandstone are intercalated (containing, from 

 the uppermost to the lowest, marine shells), the united thick- 

 ness of which is fifty feet, three of the beds of limestone 

 resting directly on the coal. Many of the forms of Equi- 

 setacea, Calamites, Sigillariae, and Ferns, are of the same 

 species as those of the west of Europe ; and the carbonife- 



