METEIORIITNCHUS. 



147 



curve towards one another till they nearly meet in the middle line ; they then diverge 

 again and die away at about the level of the hinder end of the dental series; at their 

 posterior end they may be represented by a row of foramina only. In M. moreli and 

 31. brachyrhynclius they terminate a little in front of the anterior angle of the palatal 

 vacuity. Along their median symphysis the palatine surface of the maxillae is raised 

 into a slight ridge, which in that region separates the grooves just described. Where 

 the maxillae are separated by the palatines, their palatal surface is gently concave from 

 side to side and continues to be so as far as the palatine vacuities. The posterior 

 prolongations of these bones form the outer border of the anterior portion of the 

 openings just referred to and terminate about opposite their middle point ; the alveoli 

 are continued almost to the tip of these prolongations, the upper side of which is over- 

 lapped by the anterior end of the jugals which shut out the maxilla? from any share 

 in the formation of the orbit. 



The facial surface of the maxilla is strongly convex from side to side, and a section 

 of the upper surface of the snout, in the region where the maxilhe meet in the middle 



Text-fig. 56. 



pg* als. fn 



Skull of Metriorhynehus superciliosum from right side, the palatine portions of the skull being omitted. 

 als., alisphenoid ; /., lachrymal foramen ; Jr., frontal ; j., jugal ; I., lachrymal ; l.t.f., lateral temporal 

 fossa; ma:., maxilla; n., nasals; nar., external nares ; par., parietal; pmx., premaxilla ; po.f., post- 

 frontal; pr.f., prefrontal ; pr.o., pro-otic; q., quadrate; q.j., quadrato-jugal ; sq., squamosal. 



dorsal line, makes a curve rather greater than a semicircle. This strong convexity 

 of the snout is continued in the region of the nasals, but it is only in one or two 

 specimens that this can be seen, for in nearly all cases the vertical crushing to which the 

 skulls have been subjected completely distorts their form and obscures the relations of 

 the bones to one another, especially in the neighbourhood of the orbits. The anterior 

 parts of the facial portions of the maxilla? receive between them the facial processes of 

 the premaxillse, with which they unite in a suture of varying form. Behind this they 

 may or may not meet in the mid-dorsal line to an extent differing in the different 

 species, and even to some degree in different individuals of the same species. 

 Posteriorly they are separated by the wedge-like nasals, and narrow gradually to 

 their posterior end, which is occupied by a deep groove nearly parallel with the alveolar 

 border and continued back to the deep notch on the anterior side of the lachrymal (I.), 



u2 



