274 
ELEMENTS OF GEOLOGY. 
Gres de Beauchamp, or Sahles moyens, divide the gypseous 
beds from the calcaire grossier proper. These sands, in 
which a small nummulite (iVI variolaria) is very abundant, 
contain more than 300 species of marine shells, many of them 
peculiar, but others common to the next division. 
MIDDLE EOCENE EOEMATIONS OF FEANCE. 
Calcaire Grossier, upper and middle (B. 1, p. 252).—The up¬ 
per division of this group consists in great part of beds of 
compact, fragile limestone, with some intercalated green 
marls. The shells in some parts are a mixture of Cerithium^ 
Cyclostoma, and Gorbula ; in others Limnea, Cerithiiim, Pa- 
ludina, etc. In the latter, the bones of reptiles and mamma¬ 
lia, Palmothermm and Lophiodon, have been found. The 
middle division, or calcaire grossier proper, consists of a coarse 
limestone, often passing into sand. It contains the greater 
number of the fossil shells which characterize the Paris ba¬ 
sin. No less than 400 distinct species have been procured 
from a single spot near Grignon, where they are imbedded 
in a calcareous sand, chiefly formed of comminuted shells, in 
which, nevertheless, individuals in a perfect state of preser¬ 
vation, both of marine, terrestrial, and fresh-water species, are 
mingled together. Some of the marine shells may have lived 
on the spot; but the Cyclostoma and Limnea, being land and 
fresh-water shells, must have been bi'ought thither by rivers 
and currents, and the quantity of triturated shells implies 
considerable movement in the waters. 
Nothing is more striking in this assemblage of fossil testa- 
cea than the great proportion of species referable to the ge¬ 
nus Cerithium (see Figures, p. 245). There occur no less than 
137 species of this genus in the Paris basin, and almost all of 
them in the calcaire grossier. Most of the living Cerithia 
inhabit the sea near the mouths of rivers, where the waters 
are brackish ; so that their abundance in the marine strata 
now under consideration is in harmony with the hypothesis 
that the Paris basin formed a gulf into which several rivers 
flowed. 
In some parts of the calcaire grossier round Paris, certain 
beds occur of a stone used in building, and called by the 
French geologists “ Miliolite limestone.” It is almost entire¬ 
ly made up of millions of microscopic shells, of the size of 
minute grains of sand, which all belong to the class Foram- 
inifera. Figures of some of these are given in the annexed 
Avood-cut. As this miliolitic stone neA^er occurs in the Fa- 
luns, or Upper Miocene strata of Brittany and Touraine, it 
often furnislies the geologist Avith a useful criterion for dis- 
