xv. 3 SKULL 395 



columella auris articulating with the latter. In other groups of Che- 

 Ionia, however, the dermal roofing has been reduced or 'emarginated', 

 presumably to give still better attachment for the jaw and neck muscles 



Chelone 



Trionyx 



Fig. 226. Skulls of Chelone and Trionyx. Lettering as Fig. 214, p. 377. 

 (After Goodrich from Parker and Haswell, and Zittel.) 



(Fig. 226). It has been argued that the condition in Chelone is second- 

 ary, but there is no evidence of true temporal fossae in any chelonian, 

 and since the early form *Triassochelys also had a fully roofed skull 

 there seems no reason for denying that we have here essentially an 

 anapsid condition. 



A peculiarity of recent Chelonia is the entire absence of teeth, alike 



