CRYPTODONTIA, 239 



inclines downward and forward at an open angle. This part 

 is traversed by a low obtuse median ridge, and terminates 

 below in a trenchant edentulous border. 



The nostrils are small, oval, and separated from each other 

 by the broad junction of the ascending branch of the pre- 

 max diary with them. 



The maxillary bone presents the chief peculiarity, being 

 traversed obliquely by a strong angular ridge, commencing a 

 little anterior to the orbit, and terminating at the alveolar 

 border, not far from the maxillo-premaxillary suture. The 

 alveolar border gently curves to this termination, and shows 

 no trace of a tooth or alveolus. 



The compound structure of the lower jaw is shown at the 

 fractured back part, where an upper (surangular V) element, 

 thick and rounded above, is received into an outer and lower 

 element, thin above, and thick and bent below, forming a 

 groove for the reception of the upper element. On the outer 

 side of the jaw, about the middle of the part preserved, there 

 is a longitudinal depression or narrow vacuity, above which 

 there is a low ridge. The symphysis is thick, long, and bent 

 up in the form of a beak, terminating by an edentulous sub- 

 trenchant border ; its fore and outer part is traversed by a 

 low median ridge. The length of this portion of the skull is 

 6 inches ; its breadth across the maxillary ridges is 2 inches 

 10 lines ; the extent of the symphysis of the lower jaw is 2 

 inches 6 lines. Oudcnodon is more closely allied to the 

 African bidental reptiles of the following order than to the 

 English Rhynchosaurus : so closely, in the construction of the 

 skull, as to suggest the surmise that the absence of the two 

 upper teeth may be a sexual character. 

 Genus Bhyxchosaurus, Ow. 

 Sp. Rhynchosaurus articcps, Ow.* — The fossils in which 



* Transactions of the Cambridge Philosophical Society, vol. vii., part iii., 

 1842, p. 355, plates 5 and 6. 



