120 



mentioned, toward the pit, called the distal internal longitudinal. In front of 

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

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



The cotylus of the mandible is also obliquely transverse ; the inner portion 

 deeper, in order to receive the large condyle of the quadratum 



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



The fossa for the temporal muscle is large and deep, but without inner 

 wall. The 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. The dentary terminates in a 

 peculiar striate plug, posterior to the last tooth. The distal third, or less, is 

 strongly grooved for Meckel's cartilage; proximally, this is concealed by the 

 very long laminiforni splenial. 



The splenial is largely developed on the inner face of the ramus, where 

 it articulates by ball-and-socket joint with the angular. 



The angular lias a narrow and inferior exposure on the external tace ot 

 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 above 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 for the quadratum and the 

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

 riorly, it is extensively concealed. 



The surangular is the largest bone behind the dentary. It is convex 

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

 the coronoid, thus inclosing a large shallow fossa. It supports 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 differs 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 presents the condyloid ; the 

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

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

 the alveolar margin of the dentary bone being thrown upward and outward. 



