Ch. XVIII.] MAMMIFEROUS REMAINS IN GYPSUM. 251 
from those before mentioned of the older Pliocene beds of Italy. 
We may remind those readers who are not familiar with these 
minute fossil bodies, that they belong to the order Cephalopoda, 
the animals of which are most free in their movements, and most 
advanced in their organization, of all the mollusca. The mul- 
tilocular cephalopods have been separated, by d'Orbigny, into 
two subdivisions : first, those having a syphon or internal tube 
connecting the different chambers, such as the nautilus and 
ammonite ; and, secondly, those without a syphon, to which 
the microscopic species now under consideration belong. They 
are often in an excellent state of preservation, and their forms 
are singularly different from those of the larger testacea. We 
have given a plate of some of these, from unpublished draw- 
ings by M. Deshayes, who has carefully selected the most 
remarkable types of form. 
The natural size of each species figured in plate 4, is indi- 
cated by minute points, to which we call the-reader's attention, 
as they might be easily overlooked. 
Bones of quadrupeds in gypsum.— We have already con- 
sidered the position of the gypsum which occurs in the form 
of a saccharoid rock in the hill of Montmartre at Paris, and 
other central parts of the basin. At the base of that hill it 
is seen distinctly to alternate with soft marly beds of the cal- 
caire grassier, in which cerithia and other marine shells occur. 
But the great mass of gypsum may be considered as a purely 
fresh-water deposit, containing land and fluviatile shells, toge- 
ther with fragments of palm-wood, and great numbers of 
skeletons of quadrupeds and birds, an assemblage of organic 
remains which has given great celebrity to the Paris basin. The 
bones of fresh- water fish, also, and of crocodiles, and many land 
and fluviatile reptiles occur in this rock. The skeletons of mam- 
malia are usually isolated, often entire, the most delicate extre- 
mities being preserved as if the carcasses clothed with their flesh 
and skin had been floated down soon after death, and while they 
were still swoln by the gases generated by their first decompo- 
sition. The few accompanying shells are of those light kinds 
