148 ON THE DEVOLUTIONS OK 



collected skeletons of two small glires, or the genus of the dormouse 5 

 and a head of the squirrel genus. 



Our gypsum-quarries are more prolific in bones of birds than any 

 of the other layers, either anterior or subsequent to its deposite. We 

 find whole skeletons, perfect skeletons, and parts of at least ten spe- 

 cies of all the orders. 



The crocodiles of that age resembled our common crocodiles, in the 

 form of the bead, whilst in the layers of the epoch of tbe Jura forma- 

 tion, we only discover the species a-kin to the gavial. 



There has been found at Argenton a species remarkable for its com- 

 pressed teeth, with sharp edges cutting like the dentated teeth of cer- 

 tain monitors. We also see some remains in our gypsum-quarries. 



The tortoises of this age are all of fresh-water production ; some 

 belong to the sub-genus of emydes-, and there are some as well at 

 Montmartre as in the molasse of the Doidogne, of a greater magni- 

 tude than any now existing; the others are trionyces, or soft tortoises. 



This genus, which is easily distinguished by the venniculated sur- 

 face of the bones of its shell, and which now only exists in the rivers 

 of hot countries, such as the Nile, the Ganges, and the Oronoco, was 

 very plentiful in the same formations as the palaeotheria. There are a 

 vast quantity of these remains at Montmartre, and in the molasse 

 sandstone of the Dordogne, and other gravelly deposites of the south 

 of France. 



The fresh-water lakes about which these animals lived, and which 

 received their bones, nourished, besides tortoises and crocodiles, some 

 fishes and some shelly animals. All that have been collected are as 

 foreign to our climate, and even as unknown in our present waters, 

 as the palaeotheria and other contemporary quadrupeds. 



The fish even belong partly to unknown species. 



Thus, we cannot doubt but that this population, which may be 

 termed that of the middle age, — this first great production of mammi- 

 fera, has been entirely destroyed ; and in fact, wherever we discover 

 their remains, there are above them vast marine deposites, so that the 

 sea must have overwhelmed the countries which these races inhabited, 

 and has covered them for, a very considerable period. 



Were the countries thus innundated vast in extent ? The investiga- 

 tion of the ancient beds formed in their lakes has not yet enabled us 

 to decide this question. 



To the same epoch I attribute our gypsum beds, and those of .Aix 

 many of the quarries of marly stones, and the molassic sandstones, at 

 least those of the south of France. I am also disposed to assign to the 

 same period, portions of the molasses of Switzerland, and the lignites 



