CEYPTOCLEIDUS OXONIENSIS. 167 



The parietals []yar.) widen out posteriorly into lateral processes, on which are the 

 sutural surfaces overlapped by the upper ends of the dorsal processes of the squamosals 

 {sq.^), which in this genus do not appear to have met in the middle line, so that the 

 actual vertex of the skull is formed by the parietals alone. In front of the lateral 

 process the united parietals rise into a high sagittal crest, widening out again at the 

 pineal foramen, of which they form, at least the greater part of and possibly all, the 

 margin. From an examination of this region in the young skull it seems probable 

 that the parietals completely surround the pineal foramen at its inner (cranial) end, 

 while on the outer surface of the skull a portion of its anterior margin may be formed 

 by the ovei-lappiug frontals. In front of the pineal foramen the frontals widen out 

 considerably and unite at their outer ends with the postfrontals ; in front of this they 

 form the roof of the orbit, but their relations with the bones further forwards is 

 unknown, all the specimens being very imperfect in the rostral region. 



The squamosal is of the usual triradiate form (PI. IX. fig. 3} ; the slender dorsal 

 rami (sq.^) run up to the lateral processes of the parietals, with which they unite, over- 

 lapping them on the upper and probably also on the lower surface, but not meeting 

 one another in the middle line. Judging from the appearance of this portion of the 

 squamosal in the young specimen, it seems possible that it may have originally ossified 

 from a distinct centre and may therefore represent a siipratemporal. The ventral ramus 

 unites closely with the quadrate, down the outer side of which it sends a long process. 

 The anterior (zygomatic) ramus (sq.) is thin and broad ; its upper border is strongly 

 convex, the lower concave; anteriorly it bears a sutural surface for union with the 

 jugal and presumably also with the postorbital. 



The quadrate [q.) is a large bone ; its anterior face is concave from side to side, its 

 posterior face convex or flat. The upper end is embraced by the squamosal, while at 

 its lower end it bears the broad articular surface for the mandible. This surface is 

 convex from before backwards, and is imperfectly divided into a larger outer and a smaller 

 inner convexity. There is no trace of any division of this bone into two elements. The 

 premaxillce seem to have borne six teeth each ; the muzzle was probably rather more 

 pointed than in Murcenosaiinis. 



The mandible (PL IX. figs. 6, 7) is somewhat more slenderly built than in Murceiw- 

 sauriis, and the symphysis (sym.) seems to have been somewhat shorter, otherwise the 

 structure is similar. There is no trace of any division between the articular and 

 surangular, even in the youngest specimens. The postarticular region is relatively 

 smaller and especially shorter than in Murcenosaurus. There are 25 or 26 teeth on 

 either side. 



The teeth (PI. IX. fig. 7) are long, slender, and very sharply pointed ; the enamel is 

 smooth, except for a few fine ridges confined to the lower part of the inner side cf the 

 crown. In MiD'cenosaur'us (PI. III. figs. 4-6), on the other hand, the whole of the 

 crown except the tip is covered with fine longitudinal ridges ; on the anterior and 



