PEL0NEU8TES. 43 



posterior border of the orbit. Its alveolar region bears sockets for 28-30 teeth, of 

 which the first and second are small, the next four much enlarged ; behind these 

 there is a gradual reduction in size to the posterior end of the series. Within the 

 alveoli there is a line of pits marking the position of the points of the replacing 

 teeth ; in the anterior part of the bone these pits open at the bottom of a deep groove 

 which separates the alveolar border from the narrow palatal region, the inner edge of 

 which unites with the vomer both in front of and behind the internal nares, of which 

 it forms the outer edge; behind the vomer the maxilla joins the palatine for some 

 distance, but the length of this union cannot be made out, nor is it certain whether a 

 suborbital vacuity was present or not. At its hinder end the maxilla unites internally 

 with the transpalatine bone and sends back a tapering process closely united with the 

 ventral face of the jugal, but not extending back to the squamosal. The jugal (j.) 

 extends forwards above the maxilla, forming the lower border of the orbit and 

 apparently uniting with the lachrymal in front. Posteriorly it has a union with the 

 transpalatine (t.p.) on its inner side, while on its upper edge it joins the lower end of 

 the postorbital. At its hinder end it joins the squamosal in an oblique suture. The 

 postorbital {p.orb.) is a triangular bone, the base of the triangle joining the jugal in 

 front and extending for a short distance on to the upper edge of the anterior end of 

 the zygomatic bar of the squamosal ; at its narrow upper end it no doubt united with 

 the outer end of the postfrontal, thus completing the hinder border of the orbit. 



The squamosal (sq., PI. IV.) consists of (1) a broad ventral ramus, which unites 

 closely with the quadrate, overlapping its posterior face; (2) a laterally compressed 

 zygomatic bar, which runs forwards to unite with the postorbital and jugal as already 

 mentioned ; (3) a dorsal ramus, which unites with the upper border of the lateral 

 process of the parietal and probably nearly meets its fellow in the middle line at the 

 vertex of the skull. 



The quadrate (q., PI. IV.) is a massive bone which in its natural position seems to 

 have been directed downwards, outwards, and backwards. On its inner side it is 

 supported by the posterior prolongation of the pterygoid, uniting with it by suture ; it is 

 also very firmly united with the ventral ramus of the squamosal, which, as above noted, 

 makes an extensive overlap on its hinder face ; probably it was further supported by the 

 paroccipital, which either unites directly with its upper end or with the portion of the 

 pterygoid immediately adjoining; between the paroccipital process and the post-temporal 

 bar formed by the squamosal and parietal, there must have been a post-temporal fossa 

 of considerable size. The condyle for the mandible is transversely elongated and 

 curved, with the concavity forwards. The articular surface is divided into two areas 

 by a ridge which runs obliquely from the inner anterior angle to about the middle of 

 the posterior border ; the outer area is considerably the larger and is concave from side 

 to side, but convex from before backwards ; the inner area is gently convex in all 

 directions. 



g2 



