636 



MAMMALIA. 



bone (Jig. 295, 22), constitute the bony palate, or roof of the mouth. 

 The nasal bones (20, 20) complete the upper part of the face; and, 

 being in contact along the mesial line, arch over the nasal chamber. 



Fig. 294. 



The orbit is boundeci anteriorly by the lacrymal bone (c), and 

 ihejugal or malar bone (6). Its posterior boundary is generally 

 wanting, as the external angular processes of the jugal and frontal 

 bones do not meet. 



The orbital cavity is principally formed by processes derived 

 from the os frontis, the sphenoid, the lacrymal, and the malar 

 bone ; the ethmoid and the palatine rarely entering into its com- 

 position. 



The os ethmoides, the vomer, and the turbinated bones will 

 be described minutely when we speak of the olfactory apparatus, 

 which they contribute to form. 



The inferior maxilla in Mammals is characterized by two cir- 

 cumstances, which distinguish it from that of other Vertebrata. It 

 consists, in the first place, of only two lateral pieces, exactly similar 

 to each other, joined together at the chin by a symphysis in many 

 orders, but in others even this symphysis is obliterated at an early 

 age, and in the adult the two lateral halves would seem to form 

 but one piece. 



Another character peculiar to the lower jaw of a Mammal is, 

 that it is moveably articulated with the temporal bone by means of 

 a convex and undivided condyle. These marks, identifying the 



