286 DR. c. ^^'. a:ndeews ox a is^ew plesiosale [vol. Ixxviii, 



and basisphenoid has a peculiar!}^ roughened sui'face ; externally it 

 must have joined the pteiygoids, but the line of junction between 

 the two elements cannot be seen. Between the posterior inter- 

 pterygoid vacuities (^p.i.v.^ the parasphenoid becomes Y-shaped, 

 the Y being considerably above the general level of the palate ; 

 while the other arm of the Y forms a high sharp crest separating 

 the two vacuities, in front of which the bone widens out into a flat 

 plate ^vedged in between the converging anterior ends of the 

 pterygoids. These {pt) are very large bones, of the usual 

 triradiate form. The posterior wing is long, and extends back to 

 the quadrate, which is situated far back behind the level of the 

 occipital condyle : this portion of the bone is a nearly A^ertical 

 plate, with a thickened ventral border. Anteriorly it joins the 

 basis cranii, but its relations to the parasphenoid and basisphenoid 

 are obscure : it is possible that the pterj^goid may have overlapped 

 the basis cranii to a considerable extent. In front of this junction 

 the bone is wide, and its inner and outer borders are nearly 

 parallel for some distance : there is some evidence that in this 

 region there was a median longitudinal ridge on the palatal surface. 

 About opposite the middle of the interpter3^goid vacuities the outer 

 border turns sharply outwards to form the posterior border of the 

 lateral wing, and at the same time the anterior limit of the tem- 

 poral vacuit}^. Towards its outer angle this border is raised into a 

 ridge and thickened for union with the transpalatine bone, which 

 unfortunately is not preserved on either side. As already men- 

 tioned, the pterygoid unites with the parasphenoid in front of the 

 posterior interpter^^goid vacuities {p.i.v.) and, in front of this 

 again, meets its fellow in the middle line, there being no anterior 

 interpterygoid vacuit}^ such as occurs in some Plesiosaurs (for 

 instance, JP. capensis). Externally the anterior wing unites with 

 the palatine, and doubtless anteriorly joined the vomers ; but this 

 portion is broken away. 



The palatine (jjal.) unites with the outer border of the 

 anterior wing of the pterygoid, extending back to the anterior border 

 of the lateral wing. It forms the inner and anterior border of the 

 suborbital vacuity, uniting with the maxilla in front. The upper 

 surfaces of the pterygoids about opposite the level of the middle 

 of the interpterygoid vacuities unite with the bases of a pair of 

 bones, the epipterygoids, which run up towards the lower edge 

 of the parietals ; but their union with those bones has been broken, 

 in consequence of the compression that the skull has undergone. 



The quadrates (q.) unite with the pterygoids by their inner 

 border, and are extensively overlapped by the squamosals on their 

 posterior and outer sides. Their anterior face is concave from side 

 to side. The articular surface for the mandible is wide from side 

 to side and nan-ow from before backwards, thickening a little 

 towards its outer end. 



The squamosals (sq,) are of the usual triradiate form; their 

 lower limb overlaps, and unites closely with, the quadrates: the 

 anterior (zygomatic) process runs forwards, doubtless uniting with 



