Some Considerations respecting the Parietal Bone. 



321 



The 



Ichthyosaurus has parietals larger than the proper frontals 

 nasals, it will be remembered, are very long. 



Palaeohatteria shows an interparietal fissure nearly equal to the 

 antero — posterior diameter of the frontals in the middle line. The 

 Nasals are broad. 



Plesiosaurus has parietals that are longer than the frontals; there 

 are however pre- and post-frontals, and post-orbitals. 



Fig. 6. 

 Platecarpus. 



Fig. 7. 

 Archisaurus Colurus. 



Fig. 8. 

 Triceratops. 



Platecarpus (Cretaceous) has a large broad frontal but a small 

 parietal, the narrow conjoined nasals lead forward to wider pre maxillae. 

 (S. Woodward after Merriani.) 



Anchisaurus Colurus (Dinosaur; Trias) has broad frontals, and 

 parietals that are narrow superiorly, also broad nasals. 



Triceratops serratus presents an interesting extension of what 

 are considered post-frontal bones. 



Internationale Monatsschrift für Anat. u. Phys. XXI. 21 



