426 ORDERS OF MAMMALIA. 



more slender build than the Tichorhine form. The nasal 

 bones are slender, and the nostrils are separated by a partially- 

 ossified septum. The adult animal possesses neither incisor 

 nor canine teeth. Like the preceding, R. hemitcechus is ex- 

 clusively Post-Pliocene in its distribution, and is found in 

 cave-deposits and in the Thames-valley Brick-earths. 



The Rhinoceros megarhinus of Christol ( = the R, leptorhinus 

 of Cuvier and Falconer) is also bicorn, and resembles R. hemi- 

 tachus in being of comparatively slender build. It is dis- 

 tinguished, however, by the enormous development of the 

 nasal bones and the absence of the " cloison " or bony parti- 

 tion between the nostrils. This form (fig. 350) is found in the 

 Pliocene beds of Italy and France, and also occurs in the 

 prae-glacial forest-bed of Cromer and the Lower Brick-earths 

 of the Thames valley. 



Rhinoceros Etruscus is also bicorn, and has the nostrils par- 

 tially separated by a " demi-cloison " or incomplete bony par- 

 tition, which "strengthened the basement of the anterior horn." 

 This species is found in deposits of Pliocene age, and occurs 

 also in the Post-Pliocene (as in the Cromer forest-bed). 



In the Miocene period occur various remains of hornless 

 species of Rhinoceros, which have often been united into a 

 separate genus, or sub-genus, under the name of Acerotherium. 

 Some of these forms have all the feet three-toed, and they 

 constitute the Rhinoceros incisivus of Cuvier. The typical 

 species of Acerotherium, on the other hand, are stated to agree 

 with the living Tapirs in having the fore-feet four-toed. 



Fam. 2. Tapiridce. The Tapirs are characterised by the 

 possession of a short movable proboscis or trunk. The skull 

 is pyramidal, and the nasal bones project over the nasal cavity. 

 The skin is hairy and very thick. The tail is extremely short. 

 The fore-feet have four toes each, but these are unsymmetrical, 

 and the hind-feet have only three toes, all encased in hoofs. 



The jaws are furnished with incisor teeth, (- -), small can- 



7 7 3 3 



ines, and , , molars. 



The genus Tapirus, including the existing Tapirs, appears for 

 the first time in deposits of Miocene age, and is represented 

 by various species in Pliocene and Post-Pliocene strata. The 

 genus Lophiodon comprises Tapiroid Ungulates, which are 

 essentially, if not exclusively, of Miocene age. They differ 

 from the Tapirs almost solely in the characters of some of the 

 molar and prsemolar teeth. Lastly, the genus Coryphodon, 

 likewise nearly related to the Tapirs, is found exclusively in 

 the Eocene Tertiary. 



