PECORA 307 
from various Miocene and Pliocene deposits appear to connect the 
modern Tragulina so closely with Gelocus (p. 294), and thus with 
the ancestral Cervidw, that their classification is almost an impossi- 
bility. Thus Leptomeryx, from the Miocene of the United States, 
is regarded as a Traguloid, having four premolars in each jaw 
and with the metatarsals fused into a cannon-bone. Prodremotherium, 
of the Upper Eocene Phosphorites of France, differs in that the 
metacarpals also form a cannon-bone; while in the American 
Hypertragulus, both metacarpals and metatarsals remain separate. 
Bachitherium, of the French Phosphorites, apparently presents 
affinity with Gelocus, Prodremotherium, and Dorcatherium. In this 
genus the first of the four lower premolars assumes the character 
and function of a canine, the true canine being incisor-like, and 
there are traces of minute upper incisors. 
PECORA, OR COTYLOPHORA. 
No premaxillary teeth or caniniform premolars. Upper canines 
generally absent, though sometimes largely developed. Inferior 
incisors, three on each side with an incisiform canine in contact 
with them. Molariform teeth consisting of p 3, m %, in con- 
tinuous series. Auditory bulle simple and hollow within. Odon- 
toid process in the form of a crescent, hollow above. Distal 
extremity of the fibula represented by a distinct malleolar bone of 
peculiar shape, articulating with the outer surface of the lower end 
of the tibia. Third and fourth metacarpals and metatarsals con- 
fluent. Outer or lateral toes small and rudimentary, or in some 
cases entirely suppressed ; their metapodial bones never complete 
in existing forms. Navicular and cuboid bones of tarsus united. 
Horns or antlers usually present, at least in the male sex. Left 
brachial artery arismg from a common innominate trunk, instead 
of coming off separately from the aortic arch as in the preced- 
ing sections. Stomach with four complete cavities. Placenta 
cotyledonous.1 
The Pecora or true Ruminants form at the present time an 
extremely homogeneous group, one of the best-defined and most 
closely united of any of the Mammalia. But, though the original 
or common type has never been departed from in essentials, varia- 
tion has been very active among them within certain limits; and 
the great difficulty which all zoologists have felt in subdivid- 
ing them into natural minor groups arises from the fact that 
the changes in different organs (feet, skull, frontal appendages, 
teeth, cutaneous glands, ete.) have proceeded with such apparent 
irregularity and absence of correlation that the different modifica- 
1 For the anatomy of this group see A. H. Garrod, Proc. Zool. Soc. 1$77, p. 2. 
