456 



MK. R. BROOM OX THE PERSISTENCE OF THE 



curtilage lies between the basipterygoid pi-ocess and the pterygoid. 

 This is the meniscus pterygoideus of Howes and Swinnerton, and 

 the element whose affinities we wish to examine. It is rather 

 longer than the face of the basipterygoid process, and, as will be 

 seen in the cross-sections given, it is of considerable thickness. 

 It completely sepaiates the pterygoid from the basisphenoid, so 

 that no part of the pterygoid is in contact with the basicranial 

 cartilage. Further, the " meniscus " has no direct relations with 

 the epipterygoid, the ptei-ygoid completely separating the one 

 from the other. To a considerable extent it is clasped by the 



Text-figure 5. 



Base of skull of embryo Agama hispida var. aculeata. Head lengtli 7 mm. Recon- 

 structed from sections. On the right side, parts of the vomer (parasphenoid)j 

 basipter3'goid process, and of the pterj-goid have been removed ; and a full view 

 is given of the mesopterj'goid. 



References to lettering in figures : — B.Pt.P. Basipterygoid process of Basisphenoid ; 

 E.P. Ectopterygoid (in J? & C of fig. 6 the element is not yet ossified where 

 sectioned) ; JE.Pt. Epipterygoid ; M.Pt. Mesopterygoid ; Mx. Maxilla ; 

 Pa. Palatine; Pmx. Premaxilla; Pt. Pterygoid; P.Vo. Prevomer; Q. Quad- 

 rate; Tr. Trabecula; Fo=Pa)S. Vomer =Parasphenoid. 



pterygoid, and the movement at the joint is between the 

 "meniscus" and the basipterygoid process and not between 

 the pterygoid and the " meniscus." In fact, it is pretty manifest 

 from the examination of this embryo alone that the element is 

 reallj^ a pterygoid element. 



The reconstruction of the base of the skull in this Agama 

 embryo shows a very interesting condition of the median basal 

 bony element which the large majority of morphologists call the 

 parasphenoid, but which I regard as the true homologue of the 

 mammalian vomer. Besides neai'ly covering over the pituitary 



