7(> Alhony Museum RrcarHs. 



unnecessary to criticise at length his views as to the " bird-like " 

 and lacertilian characters which he observes in the palate. 



Seeley C-^) in 1889 gave a somewhat lengthy account of the 

 structure of the Dicynodont skull, hut addrd little to our 

 knowledge of the deeper structures. 



In I'.XK) !(•■') gave an account of the Dicynodont ])alate, and 

 for the first time showed the real structure of the vomer, and its 

 relation to the premaxillary and si)henoid. 



As the result of the examination of specimens in the Albany 

 ^luseum, I am now able to give a complete account of the bones 

 of the b.asi-eranial axis, and of their relations to each other. 



Fig. 0, plate IV represents a median section of a skull of 

 Lj/i^frosaurtis hitirostris. The parts mapped by a continuous 

 line are drawn from a single specimen : the parts marked by 

 (lotted lines are restored from two other specimens. 



If the figure be compared with hg. 2 in my previous paper, it 

 will be seen that the premaxillary and vomer are very similar in 

 each, though the specimens belong to diiferent species. Behind 

 the vomer lies the basisphenoid. In my earlier paper I stated that 

 possibly the anterior part of this hone might be the presplienoid, 

 though I vvas unable to detect any suture between it and the part 

 wdiich is undoubtedly basisphenoid. In no specimen have I been 

 aide to tind any trace of a suture, so that it is probably advisable 

 to regard the wdij^le bone from the vomer to the basi-occipital as 

 the basi-sphenoid. In front, this bone is a thin osseous plate and 

 is clasped by the vomer along the wdiole of its anterior border. 

 Above, it articulates with the ethmoid. It gradually widens as it 

 passes backwards to articulate with ihe basi-occipital. On its 

 under side it gives an articulation to the pterygoids. 



The ethmoid bone which lies between the upper end of the 

 basi-sphenoid and the frontal is a comparatively thin plate. The 

 anterior border pi'ojects considerably into the nasal region, wdiile 

 the posterior border is hollowed out above to accommodate the 

 anterior part of the brain probably, and below^ is notched probably 

 for the optic nerves. Betw^een the ethmoid and the nasal and 

 premaxillary bones there was in all probability a large nasal septal 

 cartilage. 



The frontal bone on median section is seen to be unusually 

 thick at the part wdiere it is supported by the ethmoid. Immedi- 

 ately behind it, is seen the little preparietal bone. Between this 

 latter and the parietal is situated the large parietal or pineal 

 foramiMi. 



