184 GEOGNOSY AND GEOLOGY. 
elevations, although much more abundant in older lower regions, where they 
fill troughs or basins of the older rocks, or extend along the sea coasts. <A 
crystalline structure is not often found to exist in the rocks; and even 
sandstones and conglomerates are more rarely met with than loose sand-and 
water washed beds. The clay occurring here is always amorphous, and 
limestones sometimes exhibit traces only of crystallization. Calcareous tufa, 
that loose lime deposit from calcareous water, is here found for the first 
time. Mineral species are not numerous ; they generally consist of arsenical 
and iron pyrites, while hydrated oxydes of iron and manganese penetrate 
the rocks, and are sometimes found in separated deposits. The position of 
the stratification, generally indistinct, is mostly horizontal or hasin-shaped, 
rarely upheaved, this only taking place in the vicinity of abnormal masses. 
Peat is found in beds of much economical importance. 
The task of arranging and classifying tertiary deposits is rendered very 
difficult, by the fact that they vary so much in different localities; it 
therefore becomes necessary to have frequent reference to geognostical 
equivalence in comparing the tertiary of different regions. Special 
reference must be had to fossil remains, which, while distributed in great 
number, yet exhibit considerable local variations of form. It will be seen, 
that during this epoch of the world’s history, considerable climatic 
differences prevailed on the surface of the earth. ! 
The dicotyledonal form of plants prevails in the tertiary, and, while polyps 
become rarer, mollusca increase so as to form entire beds. Belemnites and 
ammonites have entirely disappeared; and, on the other hand, insects, fishes, 
reptiles, and mammalia, with some birds, become very conspicuous. The 
reptiles assume more familiar forms, and the mammalia are represented by 
pachyderms, none belonging to recent genera; ruminantia come next; and 
last of all, carnivora. 
These organic remains are generally in much better preservation than in 
the older formations, from not having been exposed so long to the tooth of 
time and the accompanying destructive influences. 
The views of different geologists with regard to the classification of the 
tertiary masses vary very much. Some rest it upon the different number 
and character of the contained fossils, but the method is hable to many 
sources of error. The arrangement which we shall here adopt is that of 
Hausmann and Bronn. 
Caleaire Grossier, or Coarse Limestone Formation. This 
formation, which embraces the so-called limestone as a conspicuous member, 
rests, when in normal situation, directly upon the newest cretaceous strata. 
The principal rock species are: various limestones, among them the pisolite 
lime, a ferruginous, coarse limestone, sometimes oolitic and traversed by 
streaks of clay ; a purer, compact, often sandy limestone, which often passes 
into a true shell conglomerate, a limestone slate, and a silicious limestone 
(calcaire silicieux) often containing hornstone and chalcedony, and known 
as meuliére de Paris, or French bukr stone. 
Marls, among them a sandy, argillaceous, marly lime, and marl clay, 
sometimes assuming a slaty texture. These masses are generally grey, 
614 
