224 THE FOREST LANDS OF NORTHERN RUSSIA. 
distinction between them and living races. Of land plants 
there have been found cycas-like plants, conifera, palms, 
willows, elms, and other species, exhibiting the true dico- 
tyledonous structure. Nuts allied to those of the cocoa 
and other palms have been found in the London clay, 
which belongs to this class of strata; and seeds of the 
fresh-water characeae or stoneworts, known by the name 
of gyrgonites—so named from the Greek Gyros, curved, 
and gonos, seed, which is descriptive of their form - are 
found in the same deposit. Lyell has subdivided the 
tertiary strata into four groups: named respectively the 
Eocene, found in Paris, London, and Belgium—3‘12 per 
cent. of the fossils found in which are of recent species. 
The name is composed of the Greek words Eos, the dawn, 
and kainos, recent, and was given in allusion to recent 
species beginning to appear; but it should be noted that 
the reference is to animals, and only incidentally to plants. 
The Meiocene, from Meton, less—a designation given, I 
presume, in relation to those which follow. This is found 
in Vienna, Bordeaux, Turin, &c., and contains amongst its 
fossils 18 per cent. of recent species. The Pleiocene, more 
recent, from Pleion, more; it is found in Italian and crag 
deposits, and of its fossils 41 per cent. are of recent species, 
And the Pleistocene, the most recent from Pleiston, most ; 
this is found in Sicilian deposits, and 95 per cent. of its 
fossils are recent. The nomenclature proceeds on the 
assumption that the greater the proportion of fossils found 
of species which still exist in a living state, the nearer to 
our times must have been the period of its deposit. 
The apparent uniformity of heat over the surface of 
the earth in earlier times, from the equator to the pole, 
may be attributed to the temperature of the cooling mass 
being so far in excess of any heat communicated by radia- 
tion from the sun to it that this scarcely disturbed the 
equality of the temperature anywhere. _ But subsequently 
it was otherwise, and in regard to the tertiary period, it 
is stated in the paper cited :— 
* «The chronological order we have followed has brought 
