MUR/ENOSAIJEUS. 87 



of the parietal, tlie upper edge of which it completely overlaps, meeting its fellow of the 

 opposite side in the mid-dorsal line ; this bar, formed by the union of the parietal and 

 squamosal, constitutes the hinder border of the temporal fossa. The lower arm is broad 

 and unites closely with the quadrate. The anterior (zygomatic) arm, which is broad 

 and flat, curves upwards and forwards, forming the posterior part of the single temporal 

 arcade ; in front it unites with the jugal and for a short distance along its upper border 

 with a triangular element, the jwsf orbital (jy.orb.). The ventral border of this bone joins 

 tbe jugal, while its upper angle unites in suture with the postfrontal, together with 

 which it forms the anterior boundary of the temporal fossa and the posterior border 

 of the orbit. A ridge running near the posterior edge of the postorbital becomes 

 continuous posteriorly with the upper edge of the zygomatic bar of the squamosal. 



No well-preserved specimen of the quadrate (q.) region is available for description. 

 The best shows that the articular surface for the mandible was strongly convex from 

 before backwards and that from side to side it was concave on its outer, and strongly 

 convex on its inner, half. There is no trace of a division into two elements, 

 possibly quadrate and quadrato-jugal, both helping to form the articulation, such as 

 will be noticed in the account of the skull of Trideidus. The quadrate is firmly 

 united on its inner anterior face with the posterior limb of the pterygoid, and 

 externally is overlapped by the squamosal, but tbe precise manner in which these 

 unions is effected cannot be seen. 



The jxigal (j., PI. VI. fig. 1 ; text-figs. 46, 47) is a short, broad, and roughly 

 quadrangular bone ; posteriorly it unites with the zygomatic bar of the squamosal, 

 above with the postorbital, below with the maxilla. The remaining anterior free 

 border helps to form the rim of the orbit. 



The maa;illa (mx., PI. III. figs. 2, 2 a ; PL VI. fig. 1 ; text-figs. 46, 47) consists 

 mainly of a strong alveolar region containing the sockets of 15-16 teeth, of which the 

 third, fourth, and fifth are considerably the largest ; behind these there is a diminution 

 in size towards the hinder end of the series. On the inner side of each alveolus there 

 is, as a rule, a pit, at the bottom of which the tip of the more or less developed 

 successional tooth can be seen. The facial portion of the maxilla is a broad convex 

 plate, forming the lower border of the orbit, to which, moreover, it seems to have 

 supplied an imperfect floor. The palatal region of the bone is a thin plate uniting 

 with the premaxillae in front, then with the vomer, and behind this, again, with the 

 palatines and probably also with the transverse bones. Posteriorly the maxilla joins 

 the jugal, and in front of the orbital region its upper edge unites with the broad low^r 

 end of the prefrontal. The prefrontal (pr.f.) is not well preserved in any of the 

 specimens. As just mentioned, its lower edge joins the maxilla, above which its posterior 

 border helps to enclose the orbit. The relations of the anterior edges are obscure, but 

 it appears that at its upper end it joins the frontal and anteriorly forms a small portion 

 of the border of the external narial opening. If, as is possible, the true prefrontal is 



