114 FOSSIL MAMMALIA. 



among the fossils, but their study involves a world of difficulty, 

 both in an osteological and a geological point of view. Among 

 the living ruminants, the species are by no means easily to be 

 distinguished ; for in this family, though so strongly separated 

 from all others, the inter-resemblance of its members is so great, 

 that naturalists have been forced to adopt parts of comparatively 

 little importance as generic characters : the horns, for instance, 

 an external character, variable in the same species, according 

 to sex, age, and cHmate, in form and in size, and even under 

 many of these circumstances totally wanting. 



It is easy, then, to conceive how difficult it is to pronounce 

 whether any isolated specimen belongs to an existing species or 

 not. If horns, their nuclei, or the frontal bone be wanting, 

 our judgments are always liable to doubt and uncertainty. 



The fossil ruminantia are found in the depositions of many 

 different eras. The Baron, indeed, states that he discovered 

 no remains of this kind in the gypsum of Paris, with the an- 

 cient pachydermata there incrusted. But they are coeval with 

 the lophiodons, in the calcareous fresh- water formation of 

 Orleans, which also incloses the debris of palaeotheria. They 

 become exceedingly numerous in the extensive ancient alluvial 

 strata where the elephant and rhinoceros are found, even as 

 numerous as the bones of horses. The caverns which are filled 

 with the osseous remains of carnivora also contain, at times, the 

 debris of ruminants. Finally, where they most particularly 

 abound is in those apertures which traverse certain mountains 

 in the south of Europe, and which are filled with what we have 

 already described as the osseous breccia. 



The ruminants, then, were clearly coeval with the other 

 mammifera of the ancient world ; and they existed in a nume- 

 rical proportion sufficiently great to produce an abundance of 

 their bones in various depositions. But this, which holds 

 true of the order, does not apply to all the genera which com- 

 pose it. The bones of many species of the deer and ox are 

 found abundantly among the fossils. But as for the bones of 



