OWEN ON RUMINANT QUADRUPEDS. 
465 
like that of the camel or peccavi. The Palaeotherium had a 
femur with three trochanters, an astragalus with its fore 
part unequally divided, and hoofs, three in number, on each 
foot. It most probably had a simple stomach, like the tapir 
and rhinoceros, which, amongst existing animals, most nearly 
resemble that extinct primitive hoofed quadruped, with toes 
in uneven number. 
Every species of ungulate mammal with an uneven number 
of hoofs or toes, that has been introduced into this planet 
since the eocene tertiary period, whether it have 1 hoof on 
each foot, as in the horse, 3 as in the rhinoceros, or 5 as in 
the elephant, resembles the Palaeotherium in having more 
than 19 dorso-lumbar vertebrae, which vertebrae also differ 
in number in different genera ; e. g ., 22 in the rhinoceros, 
23 in the mastodon, 27 in the hyrax. The typical Pachy- 
derm, with an odd number of hoofs, have also three tro- 
chanters on the femur, the fore-part of the astragalus un- 
equally divided, and the pattern of the grinding surface of 
the molar teeth unsymmetrical, and usually crossed by 
oblique enamel-ridges. All the existing odd-toed or perisso- 
dactyle mammals have a simple stomach and a vast 
and complex caecum ; the horned species have either a 
single horn, or two odd horns, one behind the other on the 
middle line of the head, as e. g ., in the one-horned and two- 
horned rhinoceroses. 
Every species of ungulate animal with hoofs in even num- 
ber, whether 2 on each foot, as in the giraffe and camel, 
or 4 on each foot, as in the hippopotamus, resembles the 
Anoplotherium in having 19 dorso-lumbar vertebrae, neither 
more nor less ; in having two trochanters on the femur, in 
having the fore-part of the astragalus equally divided, and in 
having the pattern of the grinding surface of the molar teeth 
more or less symmetrical. The horned species have the 
horns in one pair, or two pairs. All have the stomach more 
or less complex, and the caecum small and simple. In the hog 
the gastric complexity is least displayed : but in the peccari the 
stomach has three compartments ; and in the hippopotamus 
it is still more complex. But the most complex and pecu- 
liar form of stomach is that which enables the animal to 
cc chew the cud,” or submit the aliment to a second masti- 
cation, characteristic of the large group of even-hoofed JJugu- 
lata , called “ Ruminantia” 
These timid quadrupeds have many natural enemies ; and 
if they had been compelled to submit each mouthful of 
grass to the full extent of mastication which its digestion 
requires, before it was swallowed, the grazing ruminant would 
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