222 DR. R. W. SHUFELDT ON [Apr. 1, 



on the posterior bifurcation of the parietal bone. Either squamosal 

 articulates with the parotic process, the parietal, the rudiment of 

 the zygomatic arch, and finally contributes in a very limited degree 

 to the articulatory facette for the quadrate bone. 



This last-named element of the lateral aspect of the cranium is 

 large in Heloderma, and transversely unusually broad. Its outer 

 moiety behind is concaved in the vertical direction, while its 

 anterior face, though slightly convex, is nearly flat. Tubercular 

 eminences and depressions finish off its summit, and two obliquely- 

 placed articular facets, intended for the mandible, occupy its 

 mandibular end. 



Most Lizards have the ep2)3#er?/(702c? (columella) extending between 

 the pterygoid and the anterior edge of the prootic ; in Heloderma, 

 however, it quite reaches to the ventral suiface of the parietal. In 

 Iguana tulerculata it lacks a couple of millimetres of accomplishing 

 this ; in both of these reptiles it rests against the prootic above. 



Already I have said that the foramen viugnv.m is of good size, 

 being a transverse ellipse in outline, and that the occipital condyle 

 faintly shows the sutures upon its convexity throughout life. 



And now we pass to a consideration of some of the bones that 

 more directly enter into the formation of the brain-case. Presenting 

 notbing worthy of special remark, the basioccipital is nevertheless 

 interesting from the fact that the process it develops upon either 

 side, below the of)tic aperture, is of rnther unusual prominence and 

 size. We have already alluded to the large parotic processes ; each 

 one is formed by the exoccipital and opisthotic of the corresponding 

 side. 



A character of some value is seen iu the fact that the supra- 

 occipital fails to reach the ventral surface of the parietal by not an 

 inconsiderable interspace ; this, of course, likewise applies to its 

 lateral portions, the epiotics. More anteriorly, the prootic of either 

 side articulates both with the under surface of the parietal, as well 

 as with the superior end of the epipterygoid. Tbe several otic 

 bones mentioned appear to go to form the auditory capsule in the 

 same manner as they do in all ordinary Lizards. 



Every trace of the suture between the basioccipital and the basi- 

 sphenoid has been absorbed in skulls of adult individuals ; I find it 

 persisting, however, in the skull of an old Faranus benc/alensis, 

 and according to Parker (T. J.) this is also the case with Lacerta 

 viridis. This suture, when it persists, is generally a straight trans- 

 verse line. 



Strong basipterygoid processes with dilated ends are developed 

 on the })art of the basisphenoid, and they spring from their usual 

 points, and articulate, in a manner already described above, with 

 the pterygoids. 



Ossifications representing the parasphenoid, as well as the ali- 

 sphenoids, may be present in the skulls of fully-matured individuals. 

 They are to be found in their usual positions. 



No especial study was made of the of)enings that give exit to the 

 cranial nerves from brain-case, other than to note the facts that 

 [7<i] 



