SIMOLESTES TOEAX. 27 



and send a process between those bones and the external nares ; the other bones 

 bordering these openings cannot be determined. 



The palate is fairly well preserved, but most of the sutures are obliterated. The 

 pterygoids (pt.) are very large bones; posteriorly they run back in a strong vertically 

 compressed process for union with the quadrate ; beneath the basis cranii they meet 

 in a median suture, which probably extends forwards beneath the hinder portion of 

 the basisphenoid. The ventral edges of the quadrate processes are continued forwards 

 on the ventral face of the pterygoids as strong crest-like ridges, which bifurcate 

 anteriorly where the bones diverge from one another to form the outer border of the 

 posterior interpterygoid vacuity (p.p.v.) in the posterior region : external to these 

 ridges there is a deep concavity. As usual, the posterior interpterygoid vacuity is 

 divided longitudinally by the parasphenoid {fas.), which is here narrow ; anteriorly, no 

 doubt, it was interposed for a short distance between the pterygoids, which in front of 

 it unite in the median suture which seems to continue to their anterior extremities, 

 the anterior interpterygoid fossa being absent. The lateral ramus of the pterygoid has 

 its posterior border formed by the outer branch of the ventral ridge referred to above ; 

 at its outer end the ridge terminates in a knob, which, with a corresponding knob on 

 the transpalatine (ectopterygoid), forms a strong projection downwards from the 

 palate, The precise limits of the palatine portion of the pterygoids cannot be made 

 out, the sutures between them and the palatines and vomers being invisible ; no doubt 

 they united in front with the vomers, which can be seen to form a strong convex bar of 

 bone between the internal nares (i.nar.). The palatines (pal.) are perforated by a 

 foramen which may approximately mark their line of union with the pterygoids : 

 posteriorly they unite with the lateral rami of the pterygoids and the transpalatines ; 

 there may have been a small vacuity at the junction of the three bones. 



Mandible (PI. III. figs. 1, la). — The mandible is stout and solidly constructed, the 

 rami being deep. The symphysis (sym.) is deep but short, extending back to about the 

 fifth or sixth tooth ; it is considerably expanded from side to side and the teeth on it are 

 enlarged, and indeed are the largest in the jaw. The anterior portion of the ventral face 

 of the symphysis makes a well-marked angle of about 145° with the posterior portion, 

 which is in the same line as the ventral borders of the rami. These are convex out- 

 wards, curving in towards the articulations for the quadrates. Their ventral borders are 

 gently convex on the posterior half and concave in front, where they are continued 

 into the symphysis as strong rounded ridges. The splenial enters the ventral part of 

 the symphysis for a short distance ; posteriorly it rises gently, overlapping the anterior 

 end of the united articular-surangular. The coronoid seems to have been arranged 

 much as in Peloneustes (see p. 45), extending on the inner face of the ramus from the 

 coronoid angle, which it helps to form, to the symphysis. Its lower edge was probably 

 overlapped by the splenial, while its upper border forms a ridge parallel to the alveolar 

 border. The articular surface for the quadrate consists of two concavities separated by 



E2 



