266 PALAEONTOLOGY. 



tympanic pedicle so long, so narrow, or so freely suspended to 

 the posterior and lateral angles of the cranium. 



The general aspect of the skull differs, however, from that 

 of existing Lacertians, and resembles that of a bird or turtle, 

 which resemblance is increased by the absence of teeth. The 

 dense structure of the produced ends of the premaxillaries 

 indicates an analogy of function to the tusks of Bicynodon ; the 

 premaxillaries, a, are double, as in crocodiles and Chelonians ; 

 but most of the essential characters of the skull are those of 

 the lizard. The rami of the lower jaw are remarkable, as in 

 Bathygnathus, for their great depth, but not the least trace of a 

 tooth is discernible in the alveolar border of the dentary 

 element a. The surangular element, /, the angular e, and the 

 articular d, indicate a composition of the mandible, like that 

 in lizards. 



The indications of a dental system are much more obscure 

 in the Rhynchosaurus than in any existing Lacertian ; the 

 dentations of the upper jaw are feebler than in the chameleon, 

 and no trace of them can be detected in the lower jaw, where 

 they are strongest in the chameleon. The absence of the 

 coronoid process in the Rhynchosaurus, which is conspicuously 

 developed in all existing lizards, corresponds with the unarmed 

 condition of the jaw ; and the resemblance of the Rhyncho- 

 saurus in this respect to the Chelys ferox, would indicate that 

 the correspondence extended to the toothless condition of the 

 jaws. The resemblance of the mouth to the compressed beak 

 of certain sea-birds is produced by the bending down of the 

 curved and elongated premaxillaries, so as to be opposed to 

 the deep symphysial extremity of the lower jaw. 



There are few genera of extinct reptiles of which it is more 

 desirable to obtain the means of determining the precise modi- 

 fications of the locomotive extremities than the Rhynchosaurus. 

 The fore-limbs were short, but seemingly adapted for motion 

 on land as well as in water. The humerus was about half 



