230 



PALAEONTOLOGY. 



of sculptured plate-bones ; the 

 vacuities behind the orbits for 

 the temporal muscles are large 

 and widely open. These vacui- 

 ties are fenced externally by 

 two long and slender horizontal 

 bony bars ; the upper one is 

 formed by the mastoid (fig. 90, 

 8), and the post-frontal (12); 

 the lower one by the malar (26), 

 and squamosal (27) ; the latter 

 answering to the true zygomatic 

 arch in Mammals. The squa- 

 mosal abuts by its hinder ex- 

 panded end against the almost 

 vertical tympanic pedicle (28), 

 which gives attachment to the 

 lower jaw. This shews the 

 reptilian compound structure ; 

 29 marks the surangular, 30 

 the angular, 32 the dentary ele- 

 ment. In the side-view of the 

 skull, 22 is the premaxillary, 21 

 the maxillary, 15 the nasal — the 

 cavity below being the nostril, 



10 is the prefrontal — between 

 which and 21 is the lachrymal, 



11 is the frontal above the orbit. 

 The premaxillary teeth and cor- 

 responding premandibular ones 

 are unusually long, strong, and 

 sharp ; there are two similar 

 teeth in each maxillary ; the re- 

 maining serial teeth are smaller, 



