120 



mentioned, toward the pit, called the distal internal longltudmal. In Cront of 

 this, on the inner face of the quadrate, behind or near the origin of <he ala, 

 may be a ridge called the internal ridge. (See Plate xxxvii.) 



The cotylus of the mandible, is also obliqnely transverse ; the iinicr porlioii 

 deeper, in order to receive the large condyle of tiu- (piadratum 



The mandible, of course, partakes of the elongate form of IIk^ cranium. 



The fossa t()r tbe temporal muscle is large and deep, but without inner 

 wall. Tile coronoid process is elevated, convex, and rugose interiorly, and with 

 a deep longitudinal groove exteriorly. The superior margin of the coronoid 

 bone is longitudinally concave and obtuse. Tlie dentary terminates in a 

 peculiar striate plug, posterior to the last tooth. The distal tliird, or les.s is 

 strongly grooved itir Meckel's cartilage; proximally, this is concealed by (lie 

 very long laminiform splenial. 



The si)leni(d \s largely developed on the inner lace of the ramus, wliere 

 it articulates by ball-and-socket juint witli the angular. 



The angular has a narrow and inferior exposure on the external face of 

 the ramus, and overlaps the articular by extensive squamosal suture. Interi- 

 orly, it is a little more elevated, but only opposite to the coronoid bone ; behind 

 and aljove this it is restricted by the long anterior process of the surangular. 

 Anteriorly, it is terminated by the squamosal suture of the splenial, just below 

 the beginning of the coronoid bone. 



The articular furnishes the floor of the cotylus lor the quadrat um and tlie 

 large angular termination of the jaw. Inwardly, it is largely exposed; exte- 

 riorly, it is extensively. concealed. 



The surangular is the largest bone l)ehind the dentary. It is convex 

 externally, and sends a longitudinal ridge from the cotyhjid cavity to that of 

 the coronoid, thus inclosing a large shallow fossa. It suppoiis the outer or 

 vertical half of the articular cotylus of the mandible. 



The coronoid is a longitudinal bone attached by squamosal suture only to 

 the surangular. It is easily separated, and its form diflers in the genera. It 

 is always more obtuse anteriorly, and more projecting and aliform posteriorly, 

 where its superior margin is rolled over to the outer side. 



In the splenial articulation, the angular bone ])resents the condyloid ; the 

 splenial, the cotyloid face. The former narrows and retreats upward and 

 backward. Tlie articulation allows of a rotary motion inward and upward; 

 the alveolar margin of the dentary bone being thrown upward and (nitwiird. 



