272 
ELEMENTS OF GEOLOGY. 
gant, and one, named XipTiodon gracile (Fig. 218), was about 
the size of the chamois; and Cuvier inferred from the skele¬ 
ton that it was as light, graceful, and agile as the gazelle. * 
Fossil Footprints. —There are three superimposed masses 
of gypsum in the neighborhood of Paris, separated by inter¬ 
vening deposits of laminated marl. In the uppermost of the 
three, in the valley of Montmorency, M. Desnoyers discovered 
in 1859 many foot-prints of animals occurring at no less than 
six different levels.* The gypsum to whfch they belong 
varies from thirty to fifty feet in thickness, and is that 
which has yielded to the naturalist the largest number of 
bones and skeletons of mammalia, birds, and reptiles. I 
visited the quarries, soon after the discovery was made 
known, with M. Desnoyers, who also showed me large slabs 
in the Museum at Paris, where, on the upper planes of strat¬ 
ification, the indented foot-marks w^ere seen, while corre¬ 
sponding casts in relief appeared on the lower surfaces of 
the strata of gypsum which were immediately superim¬ 
posed. A thin film of marl, which before it was dried and 
condensed by pressure must have represented a much thick¬ 
er layer of soft mud, intervened between the beds of solid 
gypsum. On this mud the animals had trodden, and made 
impressions which had penetrated to the gypseous mass 
below, then evidently unconsolidated. Tracks of the Ano- 
plotherhmi with its bisulcate hoof, and the trilobed foot-prints 
of Palceotherium^ were seen of different sizes, corresponding 
to those of several species of these genera which Cuvier had 
reconstructed, while in the same beds were foot-marks of 
carnivorous mammalia. The tracks also of fluviatile, lacus¬ 
trine, and terrestial tortoises {Fmys^ Trionyx^ etc.) were 
discovered, also those of crocodiles, iguanas, geckos, and 
great batrachians, and the foot-prints of a huge bird, appar¬ 
ently a wader, of the size of the gastornis, to be mentioned 
in the sequel. There were likewise the impressions of the 
feet of other creatures, some of them clearly distinguishable 
from any of the fifty extinct types of mammalia of which 
the bones have been found in the Paris gypsum. The whole 
assemblage, says Desnoyers, indicate the shores of a lake, or 
several small lakes communicating with each other, on the 
borders of which many species of pachyderms' wandered, 
and beasts of prey which occasionally devoured them. The ^ 
tooth-marks of these last had been detected by palaeontolo¬ 
gists long before on the bones and skulls of Paleotheres en¬ 
tombed in the gypsum. 
* 8nr des Empreintes de Pas d’Anirnaux, par M. J. Desnoyers. Compte 
rendu de ITnstitut, 1859. 
