68 
USE OF THE TERM DEVONIAN. 
small sections, the distinctive osteological characters of the remarkable genera 
Glyptosteus, Chelonichthys and Psammolepis \ 
Returning from this digression, we cannot better conclude our present subject, 
than by reminding the reader, that the Devonian rocks of Russia are of very 
dissimilar lithological structure in different tracts of this vast empire. In one 
tract they are composed of red and green flags and marls, in another of red sand- 
stone, and in a third of magnesian limestones and marls of light and yellow 
colours ; whilst in the Second Part of this work, we shall have to speak of them, 
in the Ural Mountains, as black and calcareous slaty masses. Looking, there- 
fore, to these facts, and having further ascertained that the ichthyolites of the 
Old Red Sandstone of Scotland, and the Devonian mollusks of England and the 
Continent, are here intimately associated, we have no hesitation in adhering to 
the word “ Devonian,” and in urging geologists to follow our example. That term, 
we repeat, was adopted to prevent the confusion arising from the employment 
of the name Old Red Sandstone, so inapplicable to great tracts of Europe where 
the system prevailed, but where its existence had been unnoticed, because it con- 
tained no traces of red sandstone. In the preceding pages we have offered strong 
reasons for the use of the new term in Russia, by pointing out that great portions 
of the deposits of this age, which are there neither red nor sandy, contain those 
forms of extinct life which have been published and adopted as Devonian types. 
1 This drawing of the internal structure of the above-named ichthyolites, and sketches of the external 
form of all the characteristic Russian species, will be given in the Third Part of this work. 
