_Calcaire grossier_ (2. _c_, Table, p. 175.).--The formation called Calcaire grossier consists of a coarse limestone, often passing into sand. It contains the greater number of the fossil shells which characterize the Paris basin. No less than 400 distinct species have been procured from a single spot near Grignon, where they are embedded in a calcareous sand, chiefly formed of comminuted shells, in which, nevertheless, individuals in a perfect state of preservation, both of marine, terrestrial, and freshwater species, are mingled together. Some of the marine shells may have lived on the spot; but the _Cyclostoma_ and _Limnea_ must have been brought 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 testacea than the great proportion of species referable to the genus _Cerithium_ (see fig. 164.). There occur no less than 137 species of this genus in the Paris basin, and almost all of them in the calcaire grossier. Now 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, the sediment of some of which gave rise to the beds of clay and lignite before mentioned; while a distinct freshwater limestone, called calcaire siliceux, which will presently be described, was precipitated from the waters of others situated farther to the south. [Illustration: Fig. 164. Cerithium cinctum.[194-A]] [4 Illustrations: EOCENE FORAMINIFERA. Fig. 165. _Calcarina rarispina_, Desh. _b_. natural size. _a_, _c_. same magnified. Fig. 166. _Spirolina stenostoma_, Desh. B. natural size. A, C, D. same magnified. Fig. 167. _Triloculina inflata_, Desh. _b_. natural size. _a_, _c_, _d_, same magnified. Fig. 168. _Clavulina corrugata_, Desh. _a_. natural size. _b_, _c_. same magnified.] 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 entirely made up of millions of microscopic shells, of the size of minute grains of sand, which all belong to the class Foraminifera. Figures of some of these are given in the annexed woodcut. As this miliolitic stone never occurs in the Faluns, or Miocene strata of Brittany and Touraine, it often furnishes the geologist with a useful criterion for distinguishing the detached Eocene and Miocene formations, scattered over those and other adjoining provinces. The discovery of the remains of Paleotherium and other mammalia in some of the upper beds of the calcaire grossier shows that these land animals began to exist before the deposition of the overlying gypseous series had commenced.