468 



ANATOMY OF VERTEBRATES. 



vertical, quadrate, expanded plate, which completes the upper 

 part of the neural canal (foramen magnum). 



The superoccipital enters into the formation of the upper sur- 

 face of the skull, as at 3, fig. 313. The parietals present flat supra- 

 cranial, ib. 7, 7, temporal, and intra-cranial surfaces, fig. 315, 7. 

 The frontals present, also, a flat supracranial surface, fig. 313, ii, 

 an orbital, and an intra-cranial surface, fig. 315, ii. The postorbital 

 process is not joined by a malar one : the superorbital canals are 

 large, as in Ruminants. The nasals, 15, are long and pointed: 

 the premaxillaries, 22, unite and circumscribe with them the ex- 

 ternal nostril. There is a prenasal bone, <9, which strengthens 

 the uprooting snout in most of the hog-tribe. The maxillary, 21, 



315 



Section of Skull of Young Pig {Sus\ 



in the adult Boar, developes a large outwardly-curved alveolus 

 for the tusk ; strengthened above, in the Indian wild Boar, by a 

 longitudinal ridge : the antorbital perforation is of moderate size : 

 the maxillary unites posteriorly with the large facial plate of the 

 lacrymal, fig. 313, 73, and with the malar, 2f. This has no post- 

 orbital process. It is united with the zygomatic part of the squa- 

 mosal, 27, by a double notch. The small cranial plate of the 

 squamosal is shown at d, fig. 315. The articular surface for the 

 mandible is convex from before backward, concave transversely, 

 in which direction it is most extended. The alisphenoid is marked 

 /, in figs. 313 and 315. The floor and sides of the long nasal 

 canal are formed by the premaxillaries, fig. 315, 22, the maxillaries, 

 21, and the palatines, 20 : to the latter succeed the pterygoids,/: 

 the depth of the canal is gained by depressing the backwardly- 



