158 MARLXE REPTILES OF THE OXFORD CLAY. 



Towards their posterior end they thin away, but the exact form of this end is not 

 known. On the outer surface they unite with the dentary, and at their posterior end are 

 overlapped by the anterior prolongations of the surangular and angular (any.). They 

 extend beneath the latter for some distance anteriorly, forming the ventral border 

 of the ramus. On their upper edge they bear a narrow groove which lodges the 

 slender anterior prolongation of the coronoid (cor.) ; the outer margin of this groove 

 is formed mainly by the upper edge of the surangular, but sometimes for a short 

 distance in front the dentary shares in its formation. 



The angular {ang.) and surangular (s.ang.), which form the greater part of the 

 ramus, unite with one another on the outer side of the jaw in an overlapping suture, 

 which is not interrupted by any lateral vacuity. Anteriorly, as already noted, they are 

 overlapped externally by the hinder end of the dentary, and on the inner side unite 

 with the splenial, with which they enclose a large dental canal. At its hinder end the 

 angular is prolonged backwards to the end of the postarticular process, and its upper 

 edge unites with the articular to about the level of the hinder border of the articular 

 surface, in front of which the two are separated by a small intercalated bone, 

 apparently a prearticular (p.art., dermo-articular of Kingsley), which, so far as I am 

 aware, has not been previously recorded in Crocodiles. This element is confined to 

 the inner face of the jaw; it unites above and on its outer side with the edge of the 

 inner lobe of that part of the articular which bears the surface for the quadrate ; 

 thence it sends downwards and forwards, along a deep groove on the inner face of the 

 angular, a slender process which in no specimen is complete anteriorly, but which 

 probably reached the posterior end of the splenial. Posteriorly the bone appears as a 

 short pointed process between the articular and angular. 



The surangular (s.ang.) extends backwards nearly to the end of the postarticular 

 process, uniting closely with the articular above. In front of this its upper border 

 is thickened and rounded, running nearly horizontally forwards to the coronoid 

 angle, where it curves sharply down, the bone narrowing gradually to its anterior 

 end. On the inner edge of its upper border in this region lies the peculiar 

 coronoid (cor.). This bone, which forms the summit of the coronoid angle, where it is 

 considerably expanded, passes anteriorly into a long slender process along the upper 

 border of the jaw, resting in a groove between the upper edges of the splenial 

 and surangular ; anteriorly it may reach the dentary and for a short distance 

 border upon the inner side of the tooth-sockets. From the coronoid angle to its 

 hinder extremity the inner surface of the bone bears a roughened surface for muscle- 

 attachment. In recent Crocodiles the coronoid helps to form the coronoid angle and 

 in that region resembles the same bone in Hetriorhynclius; but beyond this the 

 resemblance ceases, for, instead of being prolonged forwards in the manner above 

 described, it spreads downwards, overlapping the inner face of the splenial in front, 



