LIASSIC PLESIOSAURS. 9 



ture, I infer from their being on the same level, and from the corresponding surfaces 

 being presented by the single arched bone (3) representing the superoccipital. This 

 has been displaced by the pressure operating not quite vertically, but with an incli- 

 nation from the left to the right, which has turned the spines of the cervical vertebrae 

 to the right, and which has so far displaced the superoccipital in the same direction 

 that it lies with its concavity or arch embracing, as it were, the right superoccipital, 

 this concavity having formed the upper half of the foramen magnum. The apex of 

 the superoccipital lies beneath the right branch of tlie parietal ; the outer surface of 

 the piers of the superoccipital arch is moderately smooth and convex ; the breadth of 

 the base of the arch is 1 inch 3 lines, that of the span of the arch is 5 lines. 



The parietal (ib., 7) is thick and transversely extended posteriorly, where it is 

 overlapped by the mastoids (s), anterior to which it contracts to form the crest be- 

 tween the temporal fossae. The crest is interrupted by the parietal foramen (/), an- 

 terior to which it is resumed for a short extent — 3 lines, before the frontal suture. 

 The total length of the parietal is 1 inch 1 1 lines ; the length of the crest is 1 inch 3 

 lines. Tlie thick and rather rugged hinder bifurcate part of the parietal is overlapped 

 or embraced by the mastoid (s), and these bones curve outward and backward to 

 articulate with the squamosal (,27) find with the tympanic (28), which is continued in 

 the same direction to the joint of the mandible (29). AH these bones together form 

 a strong arch, curved backward in the present specimen, but owing its horizontal 

 position to the posthumous pressure, and having the piers of the arch directed down- 

 ward as well as outward and backward in the natural state. 



The sutui'e between the frontals (11) remains, and that between the postfrontals 

 (12) and the expansions of the parietal {'') upon the sides of the cranium may be 

 traced. There is a smooth superorbital (11') between the rougher frontal and the orbit, 

 unless the fissure defining them be a fracture and not a suture. The external facial 

 plate of the prefrontals is rough ; it overlaps the fore part of the frontal and part of the 

 nasal, and extends to the small external nostril. The nasals (15) overlap the fore part of 

 the frontals, and extend about as far in advance of the nostrils as they do behind 

 them, continuing the median ridge from the frontals forward, in which, however, the 

 median suture is visible. The outer surface of the maxillarics and premaxillaries shows 

 a kind of granular rugosity, which subsides in the maxillary as this bone (21) extends 

 beneatli the orbit. The limits of the lacrymal (73) are not definable. The malar (26) forms 

 the hinder half of the suborbital boundary; its surface is smooth, and increases in 

 breadth to beyond the orbit, when it contracts and becomes rugous where it joins the 

 postfrontal (12) and squamosal (27). The bony boundary between the orbital and 

 temporal cavities is crushed and much cracked : but the outer end of a postfrontal or 

 postorbital is wedged into the squamous union of the malar and squamosal. The 

 latter (27), of a tri-radiate form, curves from the malar round the outer and back angle 

 of the temporal fossa, and extends backward upon the tympanic : the ray directed 



c 



