6 MAEINE EEPTILES OE THE OXEOED CLAY. 



defining a short palatine process which, however, does not reach the internal narial 

 opening. Immediately internal to the alveoli there is a deep groove, at the bottom of 

 which the tips of the replacing teeth appear ; the inner wall of the groove forms a 

 prominent ridge which, joining that of the opposite side, forms an elongated raised 

 triangular area at the middle of the anterior end of the palate. By the divergence of 

 these ridges posteriorly, a short groove is formed which is closed behind by the 

 prominent anterior end of the combined vomers. 



The upper (facial) surface of the anterior region of the premaxillae is gently convex 

 from side to side, and is roughened and marked by a number of small foramina opening 

 into short longitudinal grooves. The great facial processes at first narrow gradually, 

 but at a point about 40 cm. from the tip of the snout their sides become parallel and 



Text-fig. 1. 



Bestoration of the skull of Pliosaurus ferox from palatal surface. (E. 2680, about g nat. size.) 



a.p.v., anterior interpterygoid vacuity; hoc, basioccipital ; i.nar,, internal nares ; mx\, maxilla: pal., 

 palatine ; pal.f., foramen in the palatine ; par.p., paroccipital process ; pas., paraspbenoid ; pmx., 

 premaxilla ; p.p.v., posterior interpterygoid vacuities ; pt., pterygoid ; q., quadrate ; s.orb., suborbital 

 vacuity ; t.p., transpalatine ; v., vomers. 



continue so to their union Avith the frontals (or parietals). They are separated from the 

 external nares by a band of bone, which seems to be composed anteriorly of a process 

 of the maxilla, and behind by part of a bone here regarded as a nasal (see below). 



The maccillce (mx.) are very large bones, each bearing about twenty teeth; of these 

 the first two are small, the third and fourth very large. Behind these there is a 

 decrease in size to the ninth, but the tenth and eleventh are again large ; behind these 

 there is a gradual decrease to the end of the series, the hindmost teeth being very 

 small. Seen from the side the margin of the jaw presents a sinuous outline, the first 

 convexity being in the premaxilla, the next beneath the third and fourth maxillary 



