STENEOSATJKUS. 83 



The widest part of the united premaxillse is opposite the alveoli of the fourth pair of 

 teeth. Behind them there is a long diastema, concave from before backwards and 

 crossed at its hinder end by the maxillo-premaxillary suture ; the jaw is somewhat 

 constricted at this point. The facial surface of the premaxillse is usually marked by a 

 sculpture of vermiculate grooves. 



The maxillce (mx.) are very large bones forming the greater part of the rostrum. 

 From the point where their suture with the premaxillse crosses the alveolar border to 

 opposite the anterior angle of the nasals (about opposite the twenty-first maxillary 

 tooth in Steneosaurus leedsi) the sides of the rostrum are nearly parallel, the widening 

 being very gradual in this region, particularly in species, such as St. leedsi, with a long 

 narrow rostrum. At the level of the anterior angle of the nasals the divergence of the 

 sides of the jaw becomes more marked, but is still gradual, the passage into the post- 



Text-fig. 32. 



¥ f HJ- 



Semi-diagrammatic figure of the palatal surface of the skull of Steneosaurus durobrivensis. 



(About 1 nat. size.) 



hoc, basioccipital ; bs., basisphenoid ; car., carotid foramen : eu.l., lateral eustachian opening; eu.m., median 

 eustachian opening ; ex.o., exoccipital ; i.nar., internal nares ; j., jugal ; l.t.f., lateral temporal fossa ; 

 mx., maxilla; pal., palatine : p.fr., post frontal ; pmx., premaxillse; pt., pterygoid ; q., quadrate; 

 q.j., quadrato-jugal ; s.o.v., suborbital vacuity : tp., transpalatii.e. 



orbital region of the skull being quite a gentle one. From the hinder point of the 

 facial processes of the premaxillse to the anterior angle of the nasals the maxillae unite 

 with one another in the middle dorsal line ; behind this they unite in suture with the 

 nasals, which are thrust wedge-like between them. Behind these, again, they join the 

 lachrymals for a short distance, and then, narrowing gradually, run back beneath the 

 anterior prolongations of the jugals, terminating at a point just behind the orbits, 

 where they join, for a short distance, the transpalatine bone. It does not appear that 

 the maxillae form any part of the lower border of the orbits, being excluded by the 

 jugals and lachrymals. 



m2 



