754 
MAMMALIA. 
placenta is (a) indeciduate, and diffuse or cotyledonary ; 
or (4) deciduate and zonary. 
Ungulata Vera: ARTIODACTYLA and PERISSODACTYLA 
ARTIODACTYLA—PIGS, CAMELS, 
CHEVROTAINS, AND RUMINANTS. 
PERISSODACTYLA— TAPIRS, 
RHINOCEROS, Horsxs. 
The third and fourth digits of each 
foot are equally developed, and 
the line: halving the foot runs 
between them. 
The premolars and molars are 
usually different, but generally 
bunodont or selenodont. 
‘There are nineteen dorso-lumbar 
vertebree. 
The femur has no third trochanter. 
‘The astragalus has always equal 
articular facets for the navicular 
and for the cuboid.. The cal- 
caneum has an articular facet for 
the fibula, if that bone is fully 
developed. 
The stomach tends to be complex, 
and the caecum is small. 
The mamme are few and inguinal, 
or numerous and abdominal. 
The placenta is diffuse or cotyle- 
donary. 
There are often bony outgrowths 
from the frontals. 
There is no alisphenoid canal. 
The third digit occupies the middle 
of the foot, is largest, and is 
symmetrical on itself, so that the 
line halving the foot bisects the 
third digit. 
The premolars 
molars, 
resemble the 
There are almost always twenty- 
three dorso-lumbar vertebrae. 
The femur has a third trochanter. 
The astragalus has a large facet 
for the navicular, a small facet 
for the cuboid. The calcaneum 
.does not articulate with the 
lower end of the fibula (except 
Macrauchenia). 
The stomach is always simple, and 
the caecum is large. 
The mammez are always inguinal. 
The placenta is always diffuse. 
There are never bony outgrowths 
from the frontals, 
There is an alisphenoid canal 
transmitting the external carotid 
artery. 
Sub-Order ArtiopactyLa. Even-toed Ungulates 
_ Pigs and Hippopotamus (Suina), Camels (Tylopoda), 
Chevrotains (Tragulina), and Ruminants (Pecora) like 
Cattle and Deer. 
The general characters of this sub-order have been stated 
above in contrast to those of Perissodactyla. The equal 
development of the third and fourth digits, the fact that the 
premolars have a single lobe while the molars have two, the 
