TEMPOUAL ARCHES Oi'' THE REPTILIA. 



23 



have derived them directly from Ootylosaurs with no near 

 aHinity with later forms. 



Fortiiiuitely, as the result of the work of Sollas and others, Ave 

 now know the skull fairl}' well. In the temporal i-egion there is 

 a single supratem2:)oral fossa. Uehiiul and below the fossa are 

 two large membrane-bones, which have given rise to much 

 difference of opinion. By some, the upper bone has been looked 

 upon as the squamosal and the lower called the supratemporal. 

 Most i-ecent writers, however, have identified the lower bone 

 as the squamosal and the upper the supratemporal. I am also 



Text-fifiui'e 4. 



A. Skull of Youuffiua capensis Broom. From the type-skull, further restored 



from a second specimen. 1^ nat. size. 



B. Restoration of ^I'eater part of the skull of TJialattusaurus alexandrce 



Merriam. Fm'ther restored from Merriam's figure in the light of the 

 later researches of v. Huene. 



satisfied that it is the lower bone that is the squamosal. In an 

 extremely specialised skull like that of Iclithyosaurus the relations 

 of the bones are manifestly somewhat modified from what was the 

 primitive condition, but it is agreed by most that the two bones 

 are undoubtedly the homologues of the two bones usually found 

 behind the temporal fossa in lizards. These I have elsewhere 

 agreed are the squamosal and tabular. The supratemporal in the 

 Stegocephalians and those Cotylosaurs in which it occurs is 

 apparently merely a roofing-bone with no other important 



