348 The Creodonta. 
are no doubt the ancestors of the Centetidz ; and their later types, 
as Leptictis, approach the existing family in their dentition quite 
closely! The earlier types display great variety in their dentition, 
and give ground for distinguishing many genera. 
Two groups are easily recognized among the Leptictide. In 
the first of these the last or fourth inferior premolar is a simple 
premolariform tooth, different from the inferior true molars, and 
without any internal cusp. In the second division the fourthin 
ferior premolar is either like the true molars or approximates 
their form by the presence of an internal tubercle. To the latter 
group belongs the genus Chriacus, which from the slight deve 
opment of the fourth inferior premolar (Fig. 14) approximates tht . 
first division. The genus may, however, be improperly rel i 
to the Creodonta. 
Fig. 15. 
ible and patt 0 
Fic. 14.--Chriacus angulatus Cope, right ramus of mandible ane P 
ry bone with teeth ; iora the Wasatch beds of the Big Horn, W p true 
ice n size. Figs. 6-c natural size. Fig. æ, firs paar side; 4" 
from below; 4, ramus from external side; c, the same, a and lower 
from above. Fic. 15.—Mioclenus turgidus Cope, patt o of New Mi 
one animal, two-thirds natural size. From the Puerco beds see 
nal, from Vol. 111, Report U. S. Geol. Survey Terrs. 
e first division of the famil 
Fig. 14, 
There are seven genera of th f 
may be distinguished into two sections. In On 
are three well-developed anterior cusps of the inferior the anteri 
forming a tubercular sectorial tooth; in the other = 
nae U 
1 Enough is now known of the mammalian fauna 7 pera The 
of its decidedly Miocene and, to some degree, Eocene aes neat t 
Coki gh Tii ly the Eocene types; the Chiromys ene 
lodonta, while the closest allies of the carnivorous genus Crypto 
the Lower Miocene of France and the Middle Miocene 
descendants of the Eocene types appear to have persist 
tiles are not African but are South American. 
T 
