The Artiodactyla. 1081 
All-premolars but No. iv without internal crescent ...... Tragulide. 
88. Superior premolars 2-3-4 with internal as well as ex- 
ternal crest; a naviculocuboid bone; no superior 
incisors (Boöidea). 
Superior p. m. ii without internal crescent... .............+5 Moschide, 
Superior p. m. ii with internal crescent. 
Horns permanent, originating distinct from skull......... Girafide. 
Horns permanent, processes of the skull ............000..060- Movide. 
Sorna periodically. sheds visicissseevcvicousertadessissdenesedebes Cervidee 
Of the preceding sixteen families, ten are extinct. The six 
families with living representatives are the Suide, the Tragulide, 
the Camelidæ, the Moschide, the Cervide, the Giraffidee, and the 
Bovide.! Thus none of the primary divisions, I and II, have 
recent representatives. But few of them in fact (some Cænotheriidæ 
and Anthracotheriid) survived the Eocene epoch. Division III 
is, on the other hand, characteristic of Miocene and recent time, 
except that some specimens of Gelocus of the Tragulide have been 
found in Upper Eocene beds. Several genera of Tragulide, with 
Elotherium and Poébrotherium and Oreodon, belong to Oligocene - 
beds. 
Tubercular or bunodont molars are of prior age to selenodont 
molars, phylogenetically speaking. Of the former, the tritubercular 
type, it has been already shown, is ancestral to the quadritubercular 
type. Pantolestide are then clearly ancestral to all known Artio- 
dactyla, and are themselves probably the descendants of the lost 
Amblypoda Hyodonta, whose existence I have anticipated on hypo- 
thetical grounds. Of the remaining families which are constructed 
on the quadritubercular basis, there are two types, as represented 
in divisions II and III of the preceding table. The intermediate 
or fifth lobe is especially characteristic of Eocene Artiodactyla. 
The intermediate tubercles exist in the Pantolestidie, and one of 
them is preserved in the families of division II ; but in group 4 it 
is the posterior one, and in group AA it is the anterior one. In the 
Suide and Hippopotamidz, which are permanently bunodont, the 
intermediates are either lost or so divided as to lose their distinctive 
' Antilocapra is sometimes separated from the Bovidee as the type of a 
family, because it is said to sometimes shed its horny horn-sheath. 
This character, were it really normal, has no significance sufficient for 
the establishment of a family division, 
