Page:The Osteology of the Reptiles.pdf/104

86 from the palatal surface, except rarely just back of the premaxillae in the caimans, or in front of the pterygoids in the tomistomids. The palatines also meet in the middle line in all, sending up processes for articulation with the postorbital, and forming the floor of the respiratory canals. The prevomers form a pair of tubes above the maxillae and palatines, articulating posteriorly with a suprapalatal prolongation of the pterygoids; they are separate as usual, and do not often appear on the palatal surface. The pterygoids also meet in the middle line, in all procoelian forms completely surrounding the internal nares, which may or may not be divided by a median partition, meeting below the nasal tubes in front of them. In the early teleosaurs these openings were at the posterior border of the palatines. In the goniophilids the openings are surrounded by both palatines and pterygoids.

The pterygoids articulate posteriorly and externally with the postoptics by a narrow pillar, possibly representing the epipterygoids. There are large posterior palatine vacuities at the sides of the palatines, and, in Hylaeochampsa, an additional opening in the palate between the ectopterygoid and maxilla.

In the mandible (Fig. 69 ) the splenials meet in a median symphysis in slender jaws. The prearticular is apparently wholly absent, or fused with the angular. There is a large mandibular foramen between the angular, surangular, and dentary on the outer side, absent in the Thalattosuchia.