860 



PACHYDERMATA. 



support the unwieldy head or to tear up the 

 ground in search of food, as the hog tribe do 

 with their powerful snouts. In the young 

 animal this bone always consists of four sepa- 

 rate pieces a basal, two lateral, and a superior 

 occipital (fig. 471, c 1, r 2, c 3 :) but these soon 

 become inseparably united into one mass. 



467. 



The frontal bones are of very great extent, 

 and besides enclosing the anterior part of the 

 cranial box, form a large proportion of the 

 orbital cavity. In the young animal (Jig. 469, 

 , ) they are invariably two in number, 

 separated by a suture along the mesial line, 

 and in the American Tapir this separation is 

 permanent; but generally they become con- 

 solidated at an early age, leaving no trace of 

 their original separation. 



The cctlnnoid is, in the Pachydermata, of very 

 considerable size, proportioned to the acuteness 

 of the sense of smell with which these animals 

 are gifted. The cribriform plate holds a posi- 

 tion exactly similar to that which it presents 

 in the human subject, implanted between the 

 frontal and sphenoid bones, and testifies, by 

 its great extent of surface and the numerous 

 foramina which pierce it, that the olfactory 

 organs are highly developed. Towards the 

 nasal surface, likewise, the cethmoidal cells and 



Fig. 468. 



Skull of Hippopotamus. 

 Letters as in Fig. 465. 



Theparietalbones(figsA65,467,46Q,47l,f) 



are moderately extensive, covering the superior 

 and lateral portions of the skull. In the young 

 animal they are always separated by a mesial 

 suture, CJ'g. 469, 6, fr,) but in the adult are united 

 by the obliteration of this suture into one 

 piece, so as to appear but a single bone ; a pro- 

 vision, no doubt, for admitting the enormous 

 force of the temporal muscles to be exerted 

 without danger of divaricating the two lateral 

 halves, which might otherwise be torn asunder 

 at the line of junction. In the Tapir there is a 

 lofty interparietal crest, giving great additional 

 surface for the origin of the temporal muscles. 



Skull of R/n 

 Letters as in Fig 465. 



Fig. 469. 



Skull of a youm) Boar, Sus Scrofa, shewing the osteology J the cranium and face 



