Tertiary Mammalia. 25 



mana are represented by the Macacus Eocenus, the marsu- 

 pials by the Didelphys Colchesteri, the pachyderms by the 

 Hyracotherium cuniculus ; and these types alone indicate as 

 full a development of the mammalia as that exhibited by the 

 middle eocene strata of Hordvvell Cliff, the Isle of Wight, 

 and the gypsum of Montmartre, near Paris, where a more 

 numerous assemblage of species has been found. As the 

 mollusca of the upper and lower eocene differ considerably, 

 analogy leads us to expect that the species of mammalia of 

 these two periods (the lower and middle eocene) will differ 

 still more widely. On the other hand, the fossil quadrupeds 

 of the Limagne d'Auvergne, which I refer to an upper eocene 

 group (although some able geologists class them as lower 

 miocene), present another fauna ; and a fourth set of mam- 

 malia belong to the era of the Faluns of Touraine. Since the 

 falunian epoch the pliocene species came into existence, and 

 a large part of these also have in their turn become extinct, 

 giving place to the mammalia now co-existing with man. 



If we desire to satisfy ourselves of the superior facilities 

 we enjoy in studying the tertiary as compared to the secondary 

 mammalia, we have only to reflect on one advantage which a 

 collector of newer pliocene fossils enjoys over one who shall 

 confine his investigations to eocene or miocene remains. In 

 Owen's table of the fossil mammals of the British Isles, the 

 longest list of species is that derived from cavern deposits. 

 All these he refers, and I believe correctly, to the newer plio- 

 cene period. We know nothing of the bones which were en- 

 closed in the stalagmite of caverns in the older pliocene or 

 miocene or eocene eras ; and the same remark holds good in 

 all those parts of France, Belgium, and Germany which I 

 have visited, and equally so, I believe, in regard to the caves 

 of Brazil, Australia, and New Zealand, from which the bones 

 of extinct mammalia and birds have been derived. But if we 

 remain so ignorant of the inhabitants of caverns in all the 

 tertiary periods except the latest, how little knowledge can 

 we expect to derive from a similar source respecting the ter- 

 restrial fauna, when we carry back our inquiries to the Weal- 

 den or Carboniferous epochs ! We are as well assured that 

 land and rivers then existed, as that they exist now ; but it 

 is evident that even a slight geogi'aphical revolution or trans- 



