Prof. Owen on the genus Dicynodon. 61 



The Lacertine Sauria offered all the characters which could be distinguished in 

 the partially unshrouded fossils ; but the single intermaxillary bone and the double 

 nostrils being likewise present in most Ophidians and a few Batrachians, it became 

 necessary to inspect and compare more closely and extensively the anatomical 

 characters of the fossil crania in question in order to determine precisely their 

 immediate affinities. 



My first task, therefore, was to supervise the chiselling away of the extremely 

 hard and adherent sandstone which covered almost every part of the surface of the 

 skulls about to be described. 



The large and immoveably articulated superior maxillary bones, the strong and 

 complete zygomatic arch continued thence to the tympanic bone, were decisive 

 against the Ophidians and Batrachians ; few indeed of the existing Lacertians 

 manifest these characters so strongly developed as they were in the fossils : yet 

 other structures were brought to light, as the vertically-descending tympanic pedi- 

 cles, suspended by their upper extremity from the junction of the zygomatic and 

 mastoid bones, which added important evidence to the nasal and intermaxillary 

 characters in proof of the essential relationship of the bidental Reptiha to the La- 

 certian order. 



The broad and almost entire plate of bone, continued vertically down from the 

 bifurcated parietal to the occipital foramen, now so clearly displayed in the skull 

 of the Dicynodon lacerticeps (PI. IV. fig. 2.), was, however, a cranial modification 

 only presented by the Crocodilia in the existing class of Reptiles ; but the minor 

 deviations from the ordinary Lacertian structure are so numerous, the mode in 

 which Crocodilian and Chelonian characters are interwoven upon an essentially 

 Lacertian base is so interesting, and the individual and distinctive characters of 

 the Dicynodons so striking and peculiar, as to require for their illustration a detailed 

 and consecutive osteological description of the specimens at present worked out, in 

 which I shall indicate, as I proceed, the affinities illustrated by such characters. 



Sufficient has been said to demonstrate at least the generic distinction of the 

 ancient Reptilia of the African sandstones, which were armed with two canine 

 tusks ; and postponing for the present the consideration of the claims of the differ- 

 ent species here determined to subgeneric rank, which are most likely to be esta- 

 blished when the entire skeleton is brought to light, I shall provisionally include 

 them all under the generic name of Dicynodon*. 



* From Sis, two, and kwoSovs, a term applied by Hippocrates to the canine teeth, and expressing the 

 same idea as their common English denomination. The two teeth, which are so largely and exclusively 

 developed in the present most extraordinary Reptilia of ancient Africa, answer to the canines of Mam- 

 malia. 



VOL. VII. — SECOND SERIES. K 



