1086 The Artiodactyla. 
All the known species of this family are Old World excepting 
the single Hyopotamus americanus of Leidy. The genera Ceboch- 
ærus and Chceropotamus are from the Eocene, while the remaining 
two genera are of Miocene age. Some of the Anthracotheriums 
equaled the Rhinoceros in size,and were powerful beasts, well 
z armed with formidable canine teeth. 
The species of Hyopotamus were on 
the other hand, of inoffensive char- 
acter and had narrow compressed 
muzzles like the Jamas, but more gen- 
erally elongate. 
The ancestral genus is bunodont, 
without diastemata, and with well- 
developed canines. The hypothetical 
genus (1) is selenodont, with short 
diastema, and well-developed canines. 
The certainly known genera of 
the KIPHODONTIDÆ are four, which 
differ as follows :— 
Molars bunodont; diastemata; ca- 
nines large...... Rhagatherium Pict. 
` Molars selenodont ; diastemata ; ca- 
nines MECiUM. ..........2eeeeee ee eetee? 
Xiphodontotherium Filh. 
Molars selenodont ; no diastemata ; 
mS f canines not distinet in form.......- 3 
Fie, 2. — Pantolestes brachystomus ° uv. 
. Nat, size. From the Wasatch Xiphodon C 
b, mandibula rames wiih teatis e> Molars selenodont; no diastemata ; 
Gtstens, and partsof tibia and meta- superior canine developed ; inferior 
p. m. 4 functioning as canine. Protoreodon S. and O. 
Cryptomeryx Schl. probably belongs here. 
The relations of these genera are clearly somewhat like those of 
the preceding family. The bunodont condition of the molars of 
Rhagatherium is primitive, while its diastemata are the reverse: 
The continuous dental series of Xiphodon is primitive, while the 
detailed structure of the molars is advanced. These relations may 
be thus shown :— 
