282 
TERTIARY DEPOSITS OF WESTERN EUROPE, 
the North of France, and endeavour to apply it to the southern tracts of that 
country, — try to register along the flanks of the Pyrenees the equivalents of the 
lower beds of the basin of Paris, and many of the best geologists will still be found 
at issue. In England, it is true, a close parallel was long ago established between 
the calcaire grossier and the London clay ; but how long a period elapsed before 
the overlying mammiferous beds of the Isle of Wight were put into exact compa- 
rison with the gypsum beds of Paris ! How much reasoning upon the distribution 
of animals in contemporaneous basins was employed before theFaluns of the Loire 
and the Crag of England were proved to be of similar age' ! If such be the case 
in countries where this class of deposits has been well studied, we need scarcely 
say, that in the present state of our knowledge of Russia, it would be idle to draw 
too closely the terms of comparison between her tertiary deposits and their equi- 
valents in Western Europe. Even in extending our view from the British Isles to 
Eastern Germany, we are arrested midway by unanswered difficulties. Thus, the 
characters of the very numerous fossil contents of the great tertiary basin of Mayence 
have recently led us to infer, that some of its lowest beds, consisting of sand 
with brown coal and lignite, may represent the plastic clays of the Paris and Lon- 
don basins, because the shells in the overlying sands, if not absolutely the same 
as certain forms of the calcaire grossier, have among them, at all events, very few 
species indeed, approaching to those of existing nature ; whilst the numerous ver- 
tebrata in the upper beds of the same deposit are considered to be analogous to 
those of the gypseous strata of Paris, which are classed in the Eocene group 1 2 . 
If this view be sustained, it may have a great influence in determining the age 
of the adjacent fields of brown coal which cover such wide areas in Prussia and 
Northern Germany. Clear fossil evidences are, however, still wanting in regard to 
these deposits. Mineralogically, and in general structure, like the lowest beds of 
Mayence, they present strong analogies to the plastic clays and sands of England 
and France. M. v. Buch has, indeed, stated, on the authority of Count Munster, 
1 See Lyell on the Faluns of the Loire. Proc. Geol. Soc. vol. iii. p. 437. 
2 This view of the age of the basin of Mayence is drawn from the researches of M. Herman V. Meyer, 
M. Kaup and Prof. A. Braun. M. v. Meyer is of opinion, that the very numerous and peculiar vertebrata 
of this basin, whether described by himself or M. Kaup, may be compared with those of the gypsum beds 
of the Paris basin. They are, therefore, of the same age as the Anoplotheria beds of the Isle of Wight. 
Prof. A. Braun having classified and determined the very numerous shells, has found that a very small 
percentage can be referred to existing nature. See Memoir by Mr. Murchison, Irans. of the Brit. Assoc., 
Anno 1843. 
