in.] THE CRANIAL SKELETON, 121 



as in osseous Fishes, the actual lower jaw, consisting of a 

 dentary and other bones, suspended from the side of the 

 skull by the intervention of more than one bone. 



In the last-named group the lower jaw is suspended from 

 elements of the ear capsule (viz. the sphenotic, pterotic, and 

 pro-otic) by a bone called the Hyomandibnlar, and by other 

 bones the lowest of which is termed the Quadrate, with which 

 the uppermost part of the lower jaw articulates. The bones 

 from the hyomandibular to the quadrate (inclusive), or the 

 cartilaginous parts which in some forms may represent these, 

 are collectively termed the suspejisorium. 



FIG. no SIDE VIEW OF THE SKULL OF A LIZARD {Varanus). 



a, articular bone of mandible ; c, coronoid bone of mandible ; d, dentary ; _/", 

 frontal; f, pre frontal ; f'\ post-frontal; /, lachrymal; ;;/, malar; ntx, 

 maxilla; , nasal ; o, pro-otic; /, parietal ; pt, pterygoid ; pt ', columella, or 

 dismemberment of pterygoid ; pt" y os transversum ; pjc, pre maxilla ; q, quad- 

 rate bone ; *y, squamosal. 



A lower jaw, however, may be entirely and completely 

 absent, as is the case in the Lamprey. 

 In forms in which the skull is not osseous (as the Sharks) 

 the mandible is represented by cartilage. 



Wherever below Mammals the skull is ossified, the lower 

 jaw consists of a bone representing the lower jaw of man and 

 Mammals, together with three or four other bones forming with 

 it the actual ramus on each side ; and, in addition, there is a 

 distinct part by which this complex ramus articulates with 

 the suspending bone or bones which sustain it. 



This articular part, with the suspending bone (called the 

 " quadrate " in Birds and Reptiles) or bones (of which there 

 may be several, as in Fishes), all taken together, answers to 

 parts which are not commonly reckoned as portions of the 

 skeleton in man, namely to parts of the internal ear, i.e. to 



