or between them and the palatines, and, like the external ones, are small. There is always a remarkable posterior interpterygoidal vacuity, divided in the middle throughout by the large parasphenoid, the pterygoids meeting in front of and to a slight extent behind them.
Fig. 48. Plesiosaur skulls: A, Elasmosaurus, from the side: pm, premaxilla; m, maxilla; po, postorbital; j, jugal. B, Plesiosaurus, from the side. One sixth natural size. C, Trinacromerum, from the side: ang, angular; d, dentary; pm, premaxilla; po, postorbital; j, jugal; sur, surangular.
An anterior interpterygoidal vacuity, as also posterior palatine and other openings in the palate, may or may not be present. The internal nares are in front, sometimes very much in front, of the external nares. The coronoids are elongate bones, extending along the sides of the teeth internally and meeting each other in some forms in a median symphysis. As usual in long-faced forms, the splenials meet in a median symphysis.
