Prof. Owen on the Class Mammalia. 191 
The digit answering to the third in the pentadactyle foot is un- 
symmetrical, and forms, with that answering to the fourth, a 
symmetrical pair. If the species be horned, the horns form one 
pair or two pairs; they are never developed singly, of symmetri- 
eal form, from the median line. The post-tympanic does not 
project downward distinctly from the mastoid, nor surpersede it 
im any Artiodactyle; and the paroccipital always exceeds both 
nasal passages is more vertical and commences posterior to the 
last molar tooth. The base of the terygoid process is not per- 
forated by the ectocarotid artery. The crowns of the premolars 
are smaller and less complex than those of the true molars, usu- 
ee half of such crown. The last milk-molar is 
obed, 
Uminants; the comparatively small and simple cecum and the 
wally folded colon in all Artiodactyles, which equally indicate 
Me 
therium, &e., ! 
the now broken series of Artiodactyles, represented by the exist- 
M8 genera, Hippopotamus, Sus, Dicotyles Camelus, Auchenia, 
Moschus, Camelopardalis, Cervus, Antilope, Ovis, and Bos. 
A well-marked, and at the present day, very extensive subor- 
dinate group of the Artiodactyles, is called Ruminantia, in refer- 
yuce to the second mastication to which the food is subject after 
; having been swallowed; the act of rumination requiring a pecu- 
liarly complicated form of stomach. The Ruminants have the 
Cloven foot,’ %. e. two-hoofed digits on each foot forming a sym- 
metrical pair, as by the cleavage of a single hoof; in most spe- 
“les two small supplementary hoofed toes are added. The meta- 
fatpals of the two functional toes coalesce to form a single 
“tnon-bone,’ as do the corresponding metatarsals, The Camel- 
f have the upper incisors reduced to a single pair; 1n bi rest 
* the Ruminants the upper incisors are replaced by a callous 
+ the lower canines aré contiguous, and, save, in the Camel- 
Tribe, similar to the six lower incisors, forming part of the same 
minal series of eight teeth, between which and the molar 
ries there is a wide interval. The true molars have their 
§ Surface marked by two double crescents, the convexity 
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