Varanosauvus acutirostri.^, Droili. 307 



and the occasional presence of a siipratemporal. Varano- 

 fsanrus is thus probably tlie most primitive known memb; r of 

 the mammal-like reptiles, and is of very great interest I'rom 

 the standpoint of the origin of that group. 



Ill the paper referred to above 1 have listed the important 

 characters which are common to all South-African Therapsids 

 as follows : — 



1. There is one lateral temporal fossa bounded primitively 



by the postorbital and squamosal alone, the parietal 

 and jiigal entering later into its borders. 



2. The occiput is plate-hke. 



3. The interparittal and tabulares are on the back of the 



skull overlapping the supraoccipital. 



4. The brain-cavity is very high. 



5. The ear is very low on the side of the brain-cavity. 

 (•. There is only one temporal element, the squamosal. 



7. There are two coracoidal elements, the anterior not 



contributing to the glenoid cavity. 



8. The flat angular [notched behind]. 



9. The contact of the outer end of the stapes with the 



quadrate. 



Varanosanrus possesses all these characters except 0, from 

 whicii it differs by the presence of a minute supratcmporal, 

 which is obviously vanishing. 



No. 5 is not very definitely known in Varanosaurm, but, 

 judging from the position of the fenestra ovale, it is possessed. 



Although the angular is not actually present, the ai)pear- 

 ances of the other bones show conclusively that Vuraiio- 

 saurus had a typically Therapsid lower jaw. 



Varanosanrus thus possesses all the fundamental Therapsid 

 characters. It has also the following primitive features: — 



1. The retention of a vestigial suprateniporal. 



2. The retention of the primiiive union of the squamosal 



and pterygoid behind the quadrate. 



3. The Cotylosaurian-like basisphenoid. 



4. The deep posterior ramus of the ptervgoid. 



5. The extension of the lachrymal forward to the septo- 



maxilla. 

 G. The heavy neural arches and horizontal zygapophysial 

 articidating laces. 



7. The intercentra throughout the column. 



8. The holocephalous ribs. 



9. The expanded ribs in the pectoral region. 



10. The primitive form of the glenoid cavity. 



11. The [jrimitive humerus. 



12. The primitive type of femur. 



