560 MAMMALIAN AND REPTILIAN VOMERINE BONES. 



Addendum (added 14th Felruary, 1903). 



Since the above paper was sent off I have discovered the 

 presence of a pair of large prevomers in Titanosuchus; and also 

 a well developed pair of prevomers in a moderately large jDrimi- 

 tive Theriodont, allied to Lycosuclius, but as yet undescribed. 

 As a large pair of prevomers are known to occur in Tcipino- 

 ceplialus, the various stages in the evolution of the prevomer 

 may now be regarded as at least approximately known. From a 

 form like PareiasauruSy with a palate formed on the Rhj^ncho- 

 cephalian t3^pe, we get derived the Prototheriodonts Tainno- 

 cephalus and Titanosuchus — unfortunately as yet very imperfectly 

 known. In the next stage we find the true primitive Theriodonts 

 of the type of Lycosuclius (Proc. S. Af. Phil. Soc. 1902) with a 

 pair of moderately developed and quite distinct prevomers And 

 lastly, we have the higher Theriodont type represented by Gom- 

 phognathus and closely resembling the condition in Ornitlio- 

 rliynclms. In Gorgonops — which though veiy imperfectly known, 

 probably belongs to the Prototheriodonts, — we have the pre- 

 vomers anchylosed as in Ornitliorliynclius and JSLiniopterus (R.B., 

 7th January, 1903). 



