554 GEOLOGICAL MEMOIRS. 



guished from those countries by some palaeontological peculiarities. 

 It is true that the very superficial knowledge that we possess of 

 the fossil flora and fauna of the Altai will not enable us at present 

 to establish a comparison between these few fragments and the 

 great series of fossils found in Europe, but even the little at 

 present known appears to justify the following remarks, although 

 they may hereafter, when we know more of the subject, require 

 some modification. 



The genera Nautilus, Goniatites, and Posidonia, so ,, character- 

 istic of the carboniferous limestones of England and the Rhenish 

 provinces, appear to be entirely absent in the analogous deposits 

 of the Altai, and in the same way Strigocephalus and Murchisonia 

 which abound in the Devonian rocks of the Rhenish provinces, 

 and in Devonshire, have not here left any traces of their existence. 

 The class of fishes also is absent, or at least is by no means so 

 characteristic as in other Devonian districts. 



Now it would seem that with regard to the rarity of Cepha- 

 lopoda, the old rocks of the Altai offer analogies rather with 

 America than with Europe, since, according to the Count d'Archiac 

 and M. de Verneuil *, these fossils were much less abundant in the 

 ancient American than in the European seas. The Altai however 

 is far behind even the former in this respect, for there have only 

 been found at present, so far as I am aware, Goniatites ffe?islowii, 

 G. Listeri, G. carbonarius and G. sphcericus, fossils extending 

 over an immense area, some of them occurring in various parts of 

 Europe and in the United States, and even in India, according to 

 M. Von Buch, who has found G. Listeri on the banks of the 

 Ganges. The genus Orthoceratites is also rare in the Altai, com- 

 pared not only with its abundance in the ancient formations of 

 Europe, but even in America, where the fewness of the species 

 appears to be made up by a greater variety of generic forms. 



It would seem to result from the preceding observations that, at 

 the period of the deposit of the palaeozoic rocks of the Altai, the 

 sea presented a well-marked difference in the nature of the pelagic 

 fauna, distinguishing it in this respect from all the contem- 

 poraneous seas. This difference has stamped the fauna with a 

 peculiar character, which at the present day is to be observed in 

 northern seas, as compared with those of the temperate and tropic 

 zones, namely, 1. poverty in the number of orders, genera, and 

 species ; 2. great relative abundance of individuals ; and 3. certain 

 restrictions in the development of individual forms, compared 

 with their congeners of warmer countries. 



These three peculiarities seem in fact combined in the Altai 

 fossils, for they are not only remarkable for the fewness of the 

 genera and species, but also by a certain reduction in external 

 dimensions, so that enormous masses of rock appear to be made up 

 of a vast multitude of small fossils, the larger analogous forms of 

 the Cephalopodous and Brachiopodous families failing entirely, and 



* Geo]. Tr. 2d ser. vol. vi. p. 329. 



