300 THE PINEAL ORGAN 



mammal-like reptiles discovered in America and South Africa (Broom). 

 Thus in the middle or upper Permian period a group of higher Synapsids * 

 were evolved which are allied to the Theromorphs of America. These 

 were the large Dinocephalia, some of which were 1 6 to 1 8 ft. in length ; 

 also small rat-like animals and others with grotesquely shaped broad 

 skulls. Changes in the skull of these types, and more especially in the 

 parietal region, show transitions between reptilian and mammalian forms. 

 They not only show transitional stages in the gradual obliteration of the 

 parietal canal, but they also suggest how in certain orders of mammals 

 the canal may have been retained, or if not quite obliterated may have 

 reappeared in association with the widening of the skull which is corre- 

 lated with an increase in the size of the brain. 



Dicynodon (Fig. 205), although not directly in the line of mammalian 



P Mx-^i 



Fig. 205. — Skull of an Anomodont Reptile, Dicynodon Kolbei, Broom, 



viewed from above. 

 It shows an oval pineal foramen and narrow parietal bones, separated from 

 the temporal fossa by a backward prolongation of the post-orbital bone. 

 Although greatly specialized, Broom regards the skull as essentially similar 

 to the mammalian type. 



F. : frontal. Po. F. : post-frontal. 



IP. : interparietal. Po. O. : post-orbital. 



J. : jugular. P.P. : pre-parietal 



L. : lacrimal. P. Mx. : pre-maxilla. 



Mx. : maxilla. Pr. F. : pre-frontal. 



N. : nasal. Q. : quadrate. 



Par. : parietal. QJ. : quadratojugal. 



P.F. : pineal foramen. Sq. : squamosal. 



Tab. : tabular. 



descent, is very instructive with respect to reduction of width of the 

 parietal bones, and the diminution in the transverse diameter of the 



1 Synapsida : ay is, arch or recess — the type of cranial roof of Tetrapods in 

 which there is a single temporal fossa. 



