tion of the bases of the triangles meet at the 

 meson. The caudal portions diverge, thus 

 enclosing, with the cephalic end of the fronto- 

 parietals, a diamond-shaped area in which 

 the sphenethmoid is visible from the dorsimi. 

 (6). The prootic bones are paired and form the 

 caudal boundary of the orbits. Dorsad they 

 articulate with the fronto-parietals; ventrad 

 with the parasphenoid ; caudad with the 

 exoccipitals ; laterad with the squamosals 

 and pterygoids. 

 (7) . The vomers are two triradiate bories on the ven- 

 tral surface of the skull within the tri- 

 angular space formed by the palatines 

 (behind), the maxillaries (at the sides), and 

 the premaxiUaries (in front). The meso- 

 caudal arm of each bone bears a group of 

 small pointed teeth. The internal nostrils 

 (ental or internal nares) open between this 

 and the lateral arm. 

 (8). The premaxiUaries are two dentigerous bones 

 which form the extreme cephalic margin of 

 the upper jaw. They meet at the meson. 

 There is a short process projecting from the 

 dorsal edge of each bone. 

 (9) . The maxillaries are two long curved bones form- 

 ing the sides of the margin of the upper jaw. 

 They are wide in front where they articulate 

 with the premaxiUaries, and narrower caudad. 



(10). The quadrato-'iugals are short, toothless, comma- 

 shaped bones joined to the caudal end of the 

 maxUlaries and forming the extreme caudal 

 margin of the upper jaw. 



(11). The palatines are slender rodlike bones just 

 caudad of the vomer. They extend laterad 

 from the apex of the parasphenoid to the 

 maxillaries. 



(12). The pterygoids are triradiate bones on the ven- 

 tral side of the skull. The inner arm is the 

 shortest and is attached to the prootics. 



13 



