354 MAEINE EEPTILES OF THE OXEOED CLAT. 



Laterally the bones are thickened and bear sutural surfaces looking upwards and 

 outwards ; these are mainly for union with the palatine plates of the premaxillse, but 

 posteriorly probably also with the palatines. The posterior portion of the lateral 

 border has a smooth slightly concave edge, presumably the inner side of the internal 

 narial opening. The palatal face of the combined bones is gently convex from side to 

 side. 



The 'pteryqoids, (text-fig. 74) are peculiar in several respects, diifering considerably 

 from those of Murcenosaurus. The outer (lateral) ramus seems to have been very 

 short or absent, the transverse bone having united directly with the lateral border of 

 the body of the bone, where a facet for its reception can be seen. The main body of 

 the bone consists of a comparatively thin palatal portion and a thickened and deepened 

 posterior bar, which at its posterior end unites with the quadrate. The posterior 

 poitionofthe palatine region is narrow and is strengthened by a dorsal ridge-like 

 thickening, which is, in fact, the anterior prolongation of the thick quadrate region ; 

 the dorsal surface of this ridge, which dies aw-ay opposite the surface for the transverse 

 bone, bears a roughened facet, probably for union with the lower end of the columella 

 cranii. In front of this the palatal plate widens out and its ventral (oral) surface is 

 marked by a series of slight longitudinal grooves. Anteriorly the bone narrows and 

 becomes vertically compressed ; in this region it was probably in contact in the middle 

 line with its fellow of the opposite side for some distance {pt.s.) ; behind this point 

 backwards as far as the anterior edge of the parasphenoid the pterygoids are separated 

 by a median interpterygoid vacuity (i.p.v.). Anteriorly the extremities of the two 

 bones fitted into the pits on the posterior border of the vomers referred to above. The 

 most peculiar feature of the pterygoids in this genus is the presence on each of them 

 of a long process [pf.])-) for union with the postero-external angles of the basisphenoid 

 (and perhaps, to some extent, of the parasphenoid). These processes, which are 

 directed forwards and inwards, arise at the junction of the palatal and quadrate regions 

 of the pterygoids ; they are compressed from before backwards and their posterior face 

 is nearly flat, the anterior being convex from above downwards ; they terminate in flat 

 oblique facets which fit against the corresponding facets on the basis cranii as above 

 mentioned. The quadrate region of the pterygoid is short, stout, and somewhat com- 

 pressed from side to side ; its outer face is convex, while its inner bears a large flat 

 facet lor union with the pterygoid tuberosity of the basioccipital ; its posterior end is 

 bifurcated and has an irregular sutural surface for the inner edge of the quadrate, 

 with which it seems to have united very firmly. 



The palatines and transverse bones are not completely known. 



The C[uadrate region (text-fig. 75) presents some remarkable features. The articular 

 surface, which in other Plesiosaurians examined is formed entirely by the quadrate, is 

 in this case apparently constituted by two distinct elements. It is just possible 

 that this division may be the result of fracture ; but if so, this has occurred sym- 



