66 
DEVONIAN ICHTHYOLITES OF RUSSIA 
regions, he has been enabled to institute general comparisons, and to trace their 
resemblances and differences in various formations, over all those parts of Europe 
which geologists have explored. No naturalist, however accomplished, who is 
acquainted with one group of ichthyolites only, could afford us the knowledge 
of which we stood in need. To M. Agassiz, then, we referred all those remains 
of fishes with which our explorations in Russia had furnished us, being assured 
that it was in his power to clear away the great difficulties in which the study of 
the fragments of ichthyolites is involved. Whatever, therefore, may be the name, 
which the Russian naturalists above alluded to might be about to give to the fossil 
fishes of their own country, we trust that the nomenclature of Agassiz will be 
adopted by them, as forming part of a great scheme of ichthyolitic classification, 
which has been carried out in accordance with physical phsenomena and the dis- 
tribution of mineral masses as determined by geologists. 
Professor Agassiz acquaints us, that of the specimens which we referred to 
him there are certainly eight, and probably ten species, which are common to 
the Old Red Sandstone of Scotland and the Russian strata. “ So complete,” 
says he, “ is this identity, that the specimens of the two countries resemble each 
other to the extent of being confounded, often appearing to be the very casts 
of each other. It is rare (he adds) to find so perfect a resemblance occurring 
among specimens in the very same locality, and there cannot therefore exist the 
smallest doubt as to the geological horizon to which these fossils belong.” The 
species which are thus identical are, the Glyptosteus favosus, Ag., Chelonichthys 
Asmusii, Ag. (the name given to the strange monster mentioned p. 53), Diplo- 
pterus macrocephalus, Ag., Holopty chius Nobilissimus (Ag. Sil. Syst.), Dendrodus 
strigatus, Owen, Lamnodus biporcatus, Ag. {Dendrodus biporcatus, Owen), Cricodus 
incurvus, Ag. (Dendrodus incurvus, Owen) ; whilst two other species, Glyptosteus 
reticulatus, Ag., and Chelonichthys minor, Ag., are presumed to be the same as 
fragments which M. Agassiz possesses from the north of Scotland. 
With this striking coincidence, there are, however, great distinctions between 
the group of Russian ichthyolites of this deposit, when viewed as a whole, and 
that of the British Isles, for, as Agassiz well remarks, some of the forms most 
characteristic of the system in Scotland have no analogues even in Russia. Such 
are the Acanthodians, which division comprehends the genera Acanthodes, 
Diplacunthus, Cheiracanthus and Cheirolepis, and the genera Pterichthys and Cepha- 
laspis of the group of Coccosteini of that author. Nor has the very common 
