208 THE FOREST LANDS OF NORTHERN RUSSIA. 
equal manner over the surface of the globe, whilst from 
the miocene period there exists in this respect a well- 
marked inequality which has become still more pronounced 
in the present day. A comparative study of the marine 
fauna collected at Bear Island leads to similar results, 
‘The Productus giganteus, P. striatus, P. punctatus, and 
P. hemisphericus, which we know to have existed in the 
mountain limestone of this island, have been found almost 
everywhere in the mountain limestone, and possessed an 
extension equivalent to that of the Knorria imbricata, of 
the Lepidodendron Velthrimianum, and of the Calamites 
radiatus, Further, two moluscs of the mountain limestone 
of Spitzbergen, Spirifer Keilhauit and Productus costatus, 
have been found also in India; and another species, the 
Productus Humbolti, in South America, so that the Polar 
species stretched then to the tropics. The presence at 
this epoch of a climate not only equal, but also warm, is 
further proved by the banks of coral which were formed 
at Spitzbergen, and also by the great dimensions of the 
arborescent cryptograms, and by the ferns with large 
fronds preserved in Bear Island.’ Thus far Dr Heer. 
Count Saporta remarks on this :—‘ A picture so vivid, 
and so complete, beyond the interest which attaches to 
itself, is well fitted to suggest some reflections, M. Heer 
does not admit, and that with reason, that the entire earth 
has ever been submerged during the epoch of maritime 
invasion represented by the mountain limestone. He 
perceives the necessity there is for the supposition of one 
or more continents having existed, serving as an asylum 
for the plants driven back from the invaded portions, 
which then reappeared at the time of the culm, and 
of the coal, properly so called, the one class under the 
same form as before, the others represented by allied 
forms, though distinct. But M. Heer expresses astonish- 
ment that certain types were lost after the culm without 
again reappearing, although they had traversed without 
any modification the long period which just elapsed since 
the extreme base of the inferior carboniferous strata. 
