the Skull of Y)\ix(\Qmo^\ou . 295 



111 tlic middle of the parietal crest is a very small laterally 

 compressed pineal foramen. The brain-case in this region is 

 narrow even for a reptile, but it widens postei'iorly. 



The most striking characters of a side view of the skull 

 are the depressed form and the fact that the npper surface is 

 almost fiat and parallel to a line joining the teeth to the 

 articulation of the lower jaw. 



The lower border of the orbit is carried out on a rim, 

 below which the side of the face is depressed. In front of 

 the orbit is a small lachrymal foramen, and still further 

 forward two small foramina running into the maxilla 



The zygomatic arch is very deep and below the back of the 

 orbit is carried down as a powerful process which projects a 

 little outwards from the side of the face. 



Posteriorly the zygomatic arch is marked by the presence 

 of a wide smooth groove leading backwards on to the poste- 

 rior surface of the skull. 



The posterior surface of the skull consists of a median and 

 two lateral regions ; the median region is triangular, the 

 base being nearly straight and equal to about twice tlie 

 lieight. 



Projecting from the back at the lower border are the two 

 occipital condyles ; they are small, very small in proportion 

 to the size of the skull, and well se[)arated by a median 

 U-shaped notch ; they are not very well preserved. 



Lying above the condyles is the small, almost circular 

 foramen magnum, which was originally surrounded by a 

 raised rim, notched just above the condyle to form a groove 

 for the passage of the twelfth nerve. 



Placed laterally at about the level of the top of the foramen 

 magnum are two small openings, well separated irom the 

 middle line ; they are the representatives of the post- 

 temporal fossae. The whole of the back below and between 

 tiiese fossae is, viewed broadly, flat; outside them the area is 

 bounded by two deep backwardly turned flanges. Above 

 the foramen magnum the back of the skull is excavated into 

 a wide open basin, bounded on each side by the continuations 

 of the flanges which form the lateral borders of the lower 

 part of the area and by their union form the parietal crest. 



The lateral areas are separated from the median area by 

 deep V-shaped notches, which end below in the Avell-dcfincd 

 nearlv vertical groove spoken of in describing the upper 



20* 



