XX11 INTRODUCTION. 



Anthracotherium and Hippohyus, that between Choeropo- 

 tamus and Hippopotamus ; the Acerotherium was a link 

 connecting Palaeotherium with Rhinoceros. With these 

 and other forms, as Halitherium, a kind of Dugong with 

 molar teeth like those of the Hippopotamus, there like- 

 wise appear a few genera that predominate in the pliocene 

 strata, and which are still represented on the earth ; 

 though by species quite distinct from those that existed 

 during either of the tertiary periods. Our own island 

 yields but a dim and confused indication of the geological 

 operations that took place between the eocene and pliocene 

 periods, in the wreck of strata that constitute part of the 

 so-called Crag-formations on its eastern coast. In the 

 oldest, and probably miocene portion, called the " Red- 

 crag,'" numerous remains of three or four extinct species of 

 Cetaceous mammals occur ; but these were probably washed 

 out of the subjacent eocene beds. From the Red-crag 

 there have, likewise, been obtained a few rolled fragments 

 of teeth referable to a Bear, to a species of Felis of the size 

 of a Leopard, to a Hog, and a Deer. In the Norwich, or 

 fluvio-marine Crag, referred by Mr. Lyell to his oldest 

 pliocene period, there are found teeth and tusks of a Mas- 

 todon of the same species as that which is associated with 

 the Dinotherium in the miocene deposits at Eppelsheim ; 

 and no remains of Mastodon have been found in any other 

 formation in this island. This rare British Fossil Mammal, 

 occurring in a deposit which is very near, if not identical in 

 point of time, with the continental formations containing 

 more abundant and perfect remains of the same Mas- 

 todon, is a fact very analogous to that of the Choero- 

 potamus and Anoplothere in our fresh- water eocene beds ; 

 and is equally illustrative of the relation of particular 

 species to particular epochs. 



