18 MR. F. E. BEDDARB ON THE [Jan. 17, 



posterior limbs of that bone in the three types under consideration 

 are : — 



Physignathus 10:16 



Chlamydosaurus 5: 14 



Amphihohirus 6 : 17 



Chlamydosaurus and Amphiholurios are thus much closer together 

 than either is to Physignathus. 



The parietal foramen is quite different in the three types. In 

 Physignathus it is very minute; in Amphiboluras it is large and 

 longitudinally oval, and the suture between the frontal and parietal 

 bones touches the foramen equatorially. In Chlamydosauriis 

 the foramen lies much further back and is quite in the middle 

 of the anterior median piece of the parietal bone ; it is intermediate 

 in size between the foramina of the other two types. The occipital 

 region of the skull is much more depressed below the level of the 

 posterior limbs of the parietal in Physignathus than in the two 

 remaining genera. 



Anteriorly the dorsal aspect of the skull shows differences in 

 these Agamid Lizards. In both Chlamydosaurits and A mphiholurus 

 the premaxillary bone extends back beyond the posterior level of 

 the nostrils. In Physignathus the bone, which is broader than 

 in the other two tj'pes, does not extend so far back as to the 

 posterior boundary of the nostrils ; it follows that more of the 

 nostrils are bounded by the nasal bones in Physignathus than in 

 its allies. 



On the palatal aspect of the skull, Chlamydosaurus shows a 

 peculiarity which is not shared by either Amphibolurus or Phy- 

 signathus ; that is, that the pa,latines fail to meet in the middle 

 line except for a short space anteiiorly. This is not a ma,tter of 

 deficient ossification, as is shown by the clear rounded margins 

 which bound the area where the palatines do come into contact. 

 There is no question, however, here of the pterygoids pushing 

 their way in between the palatines and preventing the latter 

 from articulation, such as I have recently called attention to in 

 Uromastix S2nnip>es^. 



In none of these Lizards is there a distinctly separate postfrontal 

 bone ; nor can I detect between the occipital and the first supra- 

 temporal any rudiment of the second supratemporal. 



In all three genera, as well as in Uromastix, the columella 

 (epipterygoid) does reach the parietal bone above ; inasrauch as 

 this bone does not reach the parietal in Iguana (as noted by 

 Shufeldt t) or Phrynosoma, it seems likely that this character 

 will prove useful in distinguishing the two families Agamid?e and 

 Iguanidfe. 



In all three genera — Chlamydosaurus, Amphiholurus, and 

 Physignathus — the quadrate is directed backwards. In Iguana, 

 on the other hand, it is nearly straight, that is, at right angles 



* Supra, p. 3. 



t " Contributions to the Stiidy of Seloderma," P. Z. S. 1890, p. 222. 



