352 MAMMALIA. 



iv) seem to have formed a nearly symmetrical pair, while no. II, which 

 is shorter, is considerably turned inwards. In the manus there are also 

 rudiments of metacarpals nos. I and v, while in the pes a trace of meta- 

 tarsal no. I remains. The finest specimens of the typical species, 

 Anoplotherium commune, have been obtained from the gypsum (Upper 

 Eocene) of Montmartre, Paris. The skull measures about O3 m. in length. 

 Teeth and other fragmentary remains of this and allied species are also 

 known from the French Phosphorites and other Upper Eocene formations 

 in France, Germany, and the Isle of Wight. 



The small slender artiodactyls of the Upper Eocene and 

 Lower Miocene, which may be most probably regarded as the 

 direct ancestors of the true ruminants of later date, are variously 

 classified. So many genera are still imperfectly known, and so 

 many gradational forms occur, that it is very difficult at present 

 to suggest even a provisional arrangement. Three families, 

 however, seem to be distinguishable, and all may be described 

 as having selenodont molars. 



Of these families, that of the Caenotheriidae is perhaps the 

 most generalized. It comprises small animals with a complete 

 selenodont dentition in uniform series, and with four moderately 

 stout digits on each foot. They seem to be confined to the 

 Upper Eocene and Lower Miocene of Europe, and the typical 

 genus is 



Caenotherium (figs. 202A c). This is known by nearly complete 

 skeletons, rarely if ever more than - 3 m. in length. The skull (fig. 202) 

 exhibits an elongated facial region, usually with an irregular antorbital 

 vacuity, and the basicranial axis is slightly bent. There is a prominent 

 sagittal crest, and the tympanic bullae are large and inflated. The orbital 

 cavity is almost or completely separated from the temporal fossa by a 

 slender bar of bone. The teeth are of almost uniform height, and the 

 dental series is only interrupted sometimes by variable short diastemata 

 between the premolars. The upper molars exhibit a supplementary fifth 

 cusp between the ordinary two posterior cusps ; while the hindermost 

 lower molar is produced behind into a small third lobe. The coronoid 

 process of the mandible is excessively elongated. The ulna and radius are 

 complete and separate, and digits nos. n, v are much shorter than nos. 

 in, iv. The hind limb and foot are considerably larger than the fore limb 

 and foot, and here the lateral metapodials are not much shorter than the 

 median pair. The fibula is very slender and fused with the tibia at the 

 lower end. Ccenotherium commune is the typical species from the Lower 

 Miocene of Puy-de-D6me, France, the Mayence Basin, and Wiirtemberg. 



