30 Examination of Prof. E. Forles’s Views on the 
Mr Forbes shews farther on (p. 350), that the specific 
identity, over a certain extent, of the flora and fauna of one 
country with those of another, depends on this, that the 
countries form, or have formed, a part of the same specific 
centre ; or else on this, that they have derived their animals 
and vegetables by transmission, by means of migration over 
a continuous or very nearly approaching country—a migra- 
tion favoured, in the case of Alpine floras, by transportation 
on floating ice. The identity of the Alpine flora of the centre 
.of Europe with that of Central Asia is likewise attributed 
to the glacial epoch, and the phenomena which it occasioned ; 
but for this we have no geological proofs more positive than 
for many of the preceding assertions ; and there is nothing to 
shew that the sea of the glacial epoch extended to Central 
Asia. We know that erratic blocks and striz have not 
yet been found, either in the Ural or Altai mountains, and 
still less are they to be expected to the south of these chains, 
and in the vast plains which separate them. 
The argillaceous deposits, with blocks and beds of arctic 
shells, should be, according to the author (p. 352), contem- 
porary with a flora which came from the north, a cireum- 
stance which justifies our former observation, for these de- 
posits were formed after the extensive ice, when less land 
had emerged than now. He then inquires into the distribu- 
tion of the molluscs now living on the coasts of the British 
Islands, and follows them into remote seas, where they have 
representatives. He shews that the radiated animals have 
a distribution analogous to that of the molluscs; and, with 
regard to this fauna, considered as a whole, he is induced to 
think, that it may have had some representatives from the 
cretaceous period, and in the inferior tertiary period ; but it 
is not till the medium tertiary period, that the analogies be- 
come really remarkable. 
In speaking of the tertiary formation, we mentioned Mr 
Forbes’s memoir referring to it; and we shall here continue to 
speak only of what relates to the quaternary formation. The 
author has collected in it, in England, Scotland, and Ireland, 
124 species of shells, which, with few exception, live in the 
