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Show 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 epipterygoid(columella) extending between the pterygoid and the anterior edge of the prootic ; in Heloderma, however, it quite reaches to the ventral surface of the parietal. In Iguana tuberculata 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 magnum 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 nothing worthy of special remark, the basioccipital is nevertheless interesting from the fact that the process it develops upon either side, below the optic aperture, is of rather unusual prominence and size. W e have already alluded to the large parotic processes ; each one is formed by the exoccipital aud opisthotic of the corresponding side. A character of some value is seen in 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 Varanus bengalensis, and according to Parker (T. J.) this is also the case with Lacerta viridis. This suture, when it persists, is generally a straight transverse line. Strong basipterygoid processes with dilated ends are developed on the part 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, m a y be present in the skulls of fully-matured individuals. They are to be found in their usual positions. N o especial study was made of the openings that give exit to the crauial nerves from brain-case, other than to note the facts that |