160 Transactions of the Society. 



Many fossil forms of tapirs occur as far back as the Eocene period ; 

 others are met with in the Miocene and Pliocene formations of 

 North America ; their teeth are found in the Eed Crag of Suffolk, 

 in the Antwerp Crag, in the Lower Pliocene of Hesse-Darmstadt, 

 Austria-Hungary, France, and Italy ; one species occurring as far 

 off as in the Pliocene formation of China ; their geographical range, 

 as well as their geological antiquity, being very great. 



Among the ancestors of the horse may be mentioned the Hyra- 

 cotherium {Protorohippus venticolum), from Wyoming, in which 

 there are four toes present in the fore foot, and five toes in the hind 

 foot ; Orohippus is a closely allied genus, also from the Middle 

 Eocene of Wyoming. Palosotherium is found only in the Upper 

 Eocene of Europe, its remains having been obtained in a very 

 perfect state from Montmartre, Paris. 



Anchithcrium closely resembles Palosotherium, but the incisor 

 teeth exhibit an apical pit or depression, which characterises the 

 front teeth in the existing horse. Mesohippus is anotherearly form 

 allied to these, from the Miocene of Dakota. 



The lower Pliocene makes us acquainted with another three- 

 toed ancestor of the horse in which the crown of the worn upper 

 molar displays a more marked complexity in the folding of the- 

 enamel, and a shortening of the second and fourth digits, which 

 no longer take any part in supporting the foot on the ground. 



In Pliohippus, the second and fourth digits have lost their 

 phalangeal bones ; and only the slender splint-bones seen in the- 

 leg of the horse, represent the second and fourth digits, the= 

 animal, like the horse, being supported on the third digit alone. 



In the EmNOCEEOTiDiE we have several curious ancestral forms 

 preserved to us, of which Titanotherium, from the lower Miocene 

 of Dakota, is a remarkable example. In this animal a pair of 

 blunt bony horns are placed side by side on the nasal bones. In 

 the modern Ehinoceroses there is no bony base to the horn ; the 

 whole being composed of a mass of coalesced hair of the same 

 nature as the outer investing sheath of the cow's-horn, only the- 

 interior is solid and entirely composed of the same epidermic 

 material. Numerous fossil species of Khinoceros have been met 

 with in America, in this country, throughout Europe, and in India ; 

 and its geographical range formerly extended North, even to Arctic- 

 Siberia. Species of Rhinoceros still survive in Africa and in India. 

 One of these African species, Rhinoceros simus, is probably closely 

 related to the Rhinoceros antiquitatis, found fossil in Siberia. 



The tichorine or woolly rhinoceros is found in most English 

 bone-caves and river-deposits, and on the Dogger Bank, in the 

 North Sea, and other submerged old land-deposits off the Norfolk 

 and Suffolk coasts. In Siberia it wandered even within the Arctic- 

 Circle, its mummified remains having been discovered in the frozen 



