THEORY OF THE EARTH. 



jaw have their crescents with a simple ridge ; the 

 Xipliodons, of which the anterior molares are 

 thin and sharp on the edges, and the under pos- 

 terior, have, directly opposite the concavity of each 

 of their crescents, a point, which, on being worn, 

 also assumes the form of a crescent, so that then 

 the crescents are double as in the ruminantia ; 

 lastly, the Dichobunes, the outer crescents of 

 which are also pointed at the beginning, and 

 which have thus points disposed in pairs upon 

 their lower posterior grinders. 



The most common species in our gypsum quar- 

 ries (An. commune), is an animal of the height 

 of a boar, but much more elongated, and furnished 

 with a very long and very thick tail, so that al- 

 together it has nearly the proportion of the otter, 

 but larger. It is probable that it was well fitted 

 for swimming, and frequented the lakes in the 

 bottom of which its bones have been incrusted by 

 the gypsum which was deposited there. We have 

 one a little smaller, but in other respects pretty 

 similar (An. secundarmm.) 



We are as yet acquainted with only one ocipho- 

 don, which, however, is a very remarkable ani- 

 mal : it is that which I have named An. gracile. 

 It is slender, and delicately formed, like the pret- 

 tiest gazelle. 



There is one dichobune, nearly of the size of a 

 hare, to which I have given the name of An. le- 



