SKELETON OF THE GIRAFFE. 171 



dian line of the lieaci, one behind the other, each being 

 thus a single or odd horn. There is a well-developed 

 post-tympanic process, which is separated by the true 

 mastoid from the paroccipital in the horse, but unites 

 with the lower part of the paroccipital in the tapir, and 

 seems to take the place of the mastoid in the rhinoceros 

 and hyrax. The hinder half, or a larger proportion, of 

 the palatines enters into the formation of the posterior 

 nares, the oblique aperture of which commences in ad- 

 vance of the last molar, and, in most, of the penultimate 

 one. The pterygoid process has a broad and thick base, 

 and is perforated lengthwise by the ectocarotid. The 

 crowns of the antepenultimate, as well as the penultimate 

 and last premolars, are as complex as those of the molars ; 

 that of the last lower milk-molar is bilobed. To these 

 osteological and dental characters may be added some 

 important modifications of internal structure, as, e. ^., the 

 simple form of the stomach, and the capacious and saccu- 

 lated csecum, equally indicating the mutual affinities of 

 the odd-toed or perissodactyle hoofed quadrupeds, and 

 their claims to be regarded as a natural group of the 

 Ungulata. Many extinct genera, e. ^., lophiodon, tapio- 

 therium, pal^eotherium, hippotherium, acerotherium, ma- 

 crauchenia, elasmotherium, coryphodon, have been dis- 

 covered, which once linked together the now broken 

 series of Perissodactyla, represented by the existing 

 genera rhinoceros, hyrax, tapyrus, and equus. 



Another series of hoofed quadrupeds is characterized 

 by having their hoofs and digits in even number in both 

 fore and hind feet. The majority of these have a pair, so 

 developed as to serve as feet, and terminated by a pair of 

 hoofs so shaped as to look like one split hoof, whence the 

 name "cloven-footed," given to this predominant family of 



