1859.] OWEN REPTILIAN FOSSILS. 55 



Oudenodon Bainii, Ow. (PI. I. fig. 1.) 



In this species the back part of the skull, greatly extended in 

 breadth by the expanse of the lamelliform sinuous masto-tym- 

 panics, inclines from above the occipital condyle upward and forward, 

 the superoccipital being continued into the parietal by a longitudinal 

 channel between the occipito-teraporal cristas, whore the back part 

 passes into the upper part of the cranium. 



The temporal fossa; arc longer than they are broad, and are rela- 

 tively much longer and narrower than in the Ptychognathus ; in this 

 respect Oudenodon more resembles Dicynodon: a relatively wider space 

 is left between the temporal ridges at the upper or parietal region of 

 the cranium. The zygoma is a long, rather slender, compressed bar, 

 with its upper border directly obliquely upward and outward, its 

 inner side obliquely upward and inward. The postfrontal bar 

 dividing the temporal fossa from the orbit is directed from within 

 outward, backward and slightly downward. The interorbital space 

 is narrower than the intertemporal one, so that the lower border of 

 the orbit has a more outward position than the upper one, and the 

 aspect of the orbits is very oblique, rather more upward than out- 

 ward. The profile of the face descends by a regular curve from the 

 upper to the fore part, which is nearly vertical, — the premaxillary 

 being continued more nearly to the level of the alveolar border of the 

 maxillary than in Ptychognathus. There is a low tubercle upon the 

 prefrontal part of the orbital border ; and a somewhat larger tubercle 

 projects above the nostril. This cavity is relatively larger than in 

 Ptychognathus declivis ; and both premaxillary and maxillary are more 

 deeply notched to form its fore and under boundary : the nasal, pre- 

 frontal, and lacrymal complete that boundary. Below the middle of 

 the orbit a thick, smoothly rounded, vertical ridge projects from the 

 maxillary, in the position of the alveolus of the tusk in Pt. 

 verticalis; but it rather suddenly subsides upon the alveolar border, 

 which is here entire and imperforate, forming simply a low obtuse 

 angular projection upon that border. Sections of fragments of Owl, ,i- 

 odori have demonstrated this ridged pari of tin- maxillary to be 

 .-■.lid. without the vestige of a genu of a tooth answering to the tu>k 

 in nicynodonts. The rest of the alveolar border, chiefly formed by ' 

 the premaxillary, is toothless and subtrenchant, as in the Dicynodon! 

 reptiles ; and, the Lower jaw presenting the same structure, we have 

 in the present remarkable reptile an edentulous Saurian, as is the 

 Ehynchosaurus of the New Red Sandstone of Shropshire. 



The composition of the skull is essentially the same in Oudenodon 

 as is Dicynodon; and the same affinities maybe predicated of it. with 

 such additional approach to Ghelonia as the total absence of teeth 

 may indicate. But the double nostril and well-ossified occiput demon- 

 strate the more essential Saurian affinities of the genus. 



Oudenodon prognathus f Ow. 



as tli'- former ape tee of Oudenodon resembled tin- typical Dicyn- 

 odon in the shortness of thi face and curvatun of its contour, so tin 



