54 PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [Apr. 20, 



Ptychognathus verticalis, Ow. (PI. I fig. 2.) 

 The skull upon which this species is founded is about half the 

 size of the foregoing, from which it differs in the more vertical 

 position both of the occiput, the canines and their sockets, and the 

 premaxillary part of the skull. 



The orbits, relatively larger than in the foregoing species (which 

 may be, however, an immature character), are oval in form, as in 

 Pt. declivis ; but the long axis is in the opposite direction, viz. from 

 above downward and backward. 



The hind boundary of the orbit, formed by the postfrontal, curves 

 forward at its lower part to join the malar, leaving an entering angle 

 between it and the zygomatic part of the malar. The composition 

 of the cranium and lower jaw accords with that of the preceding 

 species. In the relative breadth of the almost flat interorbital plat- 

 form, the abrupt down-bending of the face, the small size of the 

 nostrils, the ridged canine sockets, and the general angularity of 

 the profile of the skull, the present species repeats the subgeneric 

 characters of the two foregoing kinds of Ptychognathus; and they 

 are well-marked in comparison with those species of Dicynodon 

 proper (viz. D. testudiceps and D. strigiceps) which most resemble 

 the Ptychognathus verticalis in the relative position and direction of 

 the tusks. A vertical transverse section taken across the base of 

 these tusks shows their wide pulp-cavity at that part; the thin inner 

 wall of their alveoli encroaching upon the nasal cavity; the thin sep- 

 tum narium bifurcating below ; the absence of all trace of succes- 

 sional teeth where in such sections their germ is commonly seen 

 in other Saurians ; and the great thickness of the undivided facial 

 part of the premaxillary, forming the roof of the nasal passages. 

 The bony palate is entire from the premaxillary border to a little 

 beyond the sockets of the tusks : it presents the pair of short anterior 

 ridges and the longer and more prominent median ridge behind 

 these, answering to those in the palate of Dicynodon testudiceps. 



Genus Oudenodon*, Bain. 



Mr. Andrew G. Bain, the discoverer of the bidental Reptiles 

 of South Africa, in a letter published in ' The Eastern Province 

 Monthly Magazine ' (p. 10), Graham's Town, September 1856, 

 thus notices another form of fossil Reptile occurring in formations 

 of the same age, near Fort Beaufort : — " There were many skulls 

 entirely without teeth, which we at first thought had belonged to the 

 Chelonians or Turtles ; but afterwards, finding that the animals had 

 distinct narrow ribs, which Chelonians have not, we put them down 

 also for something new, and named them ' Oudenodons,' or tooth- 

 less animals." 



Of this genus, Mr. Bain's collection, now transferred to the British 

 Museum, contains cranial evidences of two distinct species ; and a 

 third species is represented by an entire but somewhat crushed 

 cranium and lower jaw, in the collection transmitted in 1858 to the 

 British Museum by Governor Sir George Grey, G.C.B. 



* From ovSels, none, and odovs, a tooth. 



