STENEOSACETJS. 85 



ventral surface, while on the dorsal surface they send forwards, along the palatines, long 

 overlapping processes which extend at least to the level of the anterior border of the 

 orbits. Behind the narial opening the pterygoids widen out greatly, and their palatal 

 surface is hollowed into a large shallow pterygoid fossa, which is bordered by a 

 rounded ridge, most strongly developed on the posterior side. At the sides of the 

 pterygoid fossa the bones run outwards into a large lateral wing, the anterior border 

 of which is continuous internally with the edge of the palatines and externally with 

 the anterior edge of the transpalatines, the short free edge between the two helping 

 to form the hinder border of the suborbital vacuity (s.o.v.). Antero-externally the 

 lateral wing joins the transpalatine in an L-shaped suture, while posteriorly its border 

 is thickened and concave, passing externally into the large process which bears on 

 its outer face a flat roughened facet : this process does not project below the level 

 of the rest of the palatal surface to nearly the same extent as it does in the recent 

 Crocodiles, in which both the outer wing of the pterygoid and the transpalatine 

 project considerably below the level of the alveolar border. Behind the pterygoid 

 fossa the pterygoids are separated in the middle line by the wedge-shaped surface of 

 the basisphenoid (bs.), which is thrust between them, and with the sides of which they 

 unite in sutures which are usually raised into prominent ridges (text-fig. 33). In this 

 region the pterygoids form shelf-like wings along the sides of the basis cranii, the 

 wings terminating in a prominent angle a little in front of the basisphenoid- 

 basioccipital suture. At their posterior end the pterygoids send up to the sides of 

 the skull tongue-like processes, which unite with the quadrates in front and terminate 

 in a suture with the exoccipitals, which is continuous externally with that between the 

 quadrate and exoccipital. This posterior process of the pterygoid seems to help in 

 forming the anterior edge of the lateral eustachian aperture (en.L, text-fig. 33). 



The transpalatine (fp.) unites with the anterior border of the lateral wing of the 

 pterygoid in an L-shaped suture ; it then runs forwards and outwards, uniting at its 

 outer end with the jugal behind and the posterior prolongation of the palatine plate of 

 the maxilla in front. 



The nasals (n.) are large elements which unite in suture in the middle line and 

 extend forwards like a wedge between the hinder ends of the maxillae on the upper 

 surface of the skull, to a degree varying in the different species, though in all cases 

 their anterior angle is separated by a long interval from the facial processes of the 

 premaxillse. Behind their union with the maxillae, the nasals unite first with the 

 lachrymals, then with the prefrontals. Posteriorly they diverge from one another to 

 receive the more or less wedge-like anterior end of the frontals, the exact form and 

 relations of which are of much value in the determination of the species. 



The lachrymals (/.) are large triangular bones : on their inner border they join the 

 nasals, externally they unite with the maxillae, and there is usually a small lachrymal 

 (autorbital) vacuity on, or close to, the line of suture between the two bones ; the 



