Ch, XVIIL] 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 have given a plate of some of these, from unpublished draw- 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 grossier, 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 



