27 8 SKELETON OF THE EABBIT 



border of the nasal bone, and above the 

 maxilla and the anterior process of the frontal. 

 On the under surface of the skull, bounded 

 laterally by the premaxillae and maxillfe, 

 and behind by the hard palate, is a large tri- 

 angular aperture, divided longitudinally into 

 the slit-like anterior palatine foramina by the 

 palatal processes of the premaxillse, a pair of 

 thin, longitudinally rolled lamina attached 

 in front to the premaxillse, and enclosing the 

 accessory organs of smell known as Jacobson's 

 organs. 



V. Ihejugals are a pair of laterally compressed bars 

 forming the greater part of the length of the 

 zygomatic arches, which bound the orbits 

 below. Their anterior ends are fused with 

 the zygomatic processes of the maxillse, and 

 posteriorly they articulate along their dorsal 

 edges with the squamosals. 



t. Bones in relation with the mandibular arch. 



The uppermost part of ^e mandibular arch 

 gives rise to the incus and malleus, which have 

 already been described in connection with the 

 auditory capsule (p. 275). 



i. The squamosals are a pair of slightly curved 

 bony plates, which complete the side-walls 

 of the cranial cavity, lying in front of the 

 periotics, and articidating with the parietals, 

 frontals, orbito- sphenoids, and ali-sphenoids. 



From the hinder border of each squamosal 

 a slender post-tympanic process arches back- 

 wards over the external auditory meatus, lying 

 along the outer surface of the periotic. 



From the outer surface of the squamosal 

 arises a stout zygomatic process, which bears 

 on its under surface the articular facet for 

 the mandible : beyond the facet it bends down- 



