PROFESSOR OWEN, ON THE RHYNCHOSAURUS. 363 



naturally closed, and the upper and lower jaws are in close contact. 

 In this state they must originally have been buried in the sandy 

 matrix, which afterwards hardened around them : and since true Lizards, 

 owing to the uninterrupted succession of their teeth, do not become 

 edentulous by age, we must conclude that the state in which the 

 Rhynchosaurus was buried, with its lower jaw in undisturbed articu- 

 lation with the head, accorded with its natural state while living, so 

 far as the less perishable parts of its masticatory organs were con- 

 cerned. Nevertheless, since a view of the inner side of the alveolar 

 border has not been obtained, we cannot be assured of the edentulous 

 character of this very singular Saurian ; for in the Agamce and Cha- 

 meleons the dental system, seen only from the outside of the jaws, 

 appears to be represented by mere dentations of the alveolar border, 

 and the anchylosed bases of the teeth, the crowns of which really form 

 the dentations, are recognizable only by an inside view. 



But the indications of the dental system are indisputably much less 

 obvious in the Rhynchosaurus than in these existing Lacertians : the 

 dentations of the upper jaw are absolutely feebler than in the Cha- 

 meleon, and no trace of them can be detected in the lower jaw. The 

 absence of the coronoid process, which is conspicuously developed in 

 all Lizards, corresponds with the unarmed state of the jaw ; and the 

 resemblance of the Rhynchosaurus in this respect to the Chelonice, and 

 to Chelys ferox, indicates that the correspondence actually extended to the 

 edentulous condition of the jaws. The resemblance of the mouth to 

 the compressed beak of certain sea-birds, the bending down of the 

 curved and elongated intermaxillaries, so as to be opposed to the deep 

 symphysial extremity of the lower jaw, are further indications that the 

 ancient Rhynchosaur may have had its jaws incased by a bony sheath, 

 as in Birds and Turtles. 



I proceed now briefly to notice the other portions of the skeleton, 

 which, from their size, texture, and community of stratum and locality, 

 are with much probability referable to the Rhynchosaurus. 



Considerable portions of two rami of two distinct lower jaws, in 

 portions of sandstone from the Grinsill quarries, show the same struc- 



