304 PICTURESQUE SKETCHES 



During this time the land was becoming peopled 

 with all that rich variety of mammalian life, which 

 characterised the later tertiary periods in the north- 

 ern hemisphere. In addition to the elephant and 

 the Mastodon, the latter of which soon died out, we 

 have two distinct and well-marked species of rhino- 

 ceros, a hippopotamus, several kinds of horses, large 

 insectivorous animals, and a considerable number of 

 Carnivora, some of large size, and differing consider- 

 ably from the groups now inhabiting these parts of 

 the world. We also find an important and very 

 interesting group of true ruminants, including a gi- 

 gantic deer, and the aurochs, the parent, it would 

 seem, of the tribe of domestic cattle. With these 

 are associated marine Mammalia in great variety, 

 forming, on the whole, a singular and well-marked 

 group, interesting in the highest degree for the ana- 

 logies it exhibits with widely-spread existing species, 

 as well as for the differences presented between it 

 and any neighbouring fauna. 



In order, however, to give an idea of the nature 

 of the species thus forming the inhabitants of northern 

 Europe, England, northern Asia, and part of North 

 America, (for we cannot disconnect the later geolo- 

 gical history of this wide tract, including the greater 

 part of the land in the whole northern hemisphere,) 

 we must first trace the conditions under which the 

 more remarkable extinct forms of animal life are pre- 

 sented. 



Among the more singular and unexpected localities 

 for fossils of this kind, may be quoted two, very dif- 

 ferent in every other respect, but both yielding an 

 abundant supply. These are, first, the gravel cliffs at 



