Mr Owen on the Dicynodon. 335 



peculiar, as to require a detailed osteological description for 

 their complete illustration. 



In these animals, the Crocodilian structure is chiefly mani- 

 fested in the occipital region of the skull, and gives place to 

 the Lacertian characters in the upper and fore part ; but in re- 

 gard to these deviations it must be remembered, that the dis- 

 tinctive features of the Crocodilian type are most broadly 

 manifested in the existing representatives of the order, and 

 are modified and rendered less salient in the more numerous 

 and varied extinct members. 



It is necessary to bear in mind this tendency to the amal- 

 gamation of Crocodilian and Lacertian characters in the older 

 Loricata, in order to form a right estimate of the value of those 

 correspondences with the cranial peculiarities of the existing 

 Lacertians. 



Nevertheless, various characters justify the conclusion, that 

 the general type of cranial organisation manifested by modern 

 lizards, was that in which the peculiar modifications of the 

 Dicynodon have been superinduced. It is not, however, 

 amongst the modern lizards that we find the nearest approxi- 

 mation to the Dicynodon. For this we must go as far back 

 into the period of Reptilian life on this planet as the epoch of 

 the new red sandstone, when the Bhi/nchosaurus manifested 

 the Lacertian type of skull, combined with toothless jaws, 

 which were most probably sheathed with horn. What con- 

 cerns us most in the present inquiry, is the anomalous edentu- 

 lous sharp edge of the upper and lower jaws in the ancient 

 Rhynchosaur, and the Chelonian form of the deep lower jaw, 

 the same anomaly having been repeated in the extinct African 

 lizard, of apparently as remote a period, with the superaddi- 

 tion of Mammalian canine tusks. For the rest, much difi^er- 

 ence of form is manifested in the two extinct genera ; but it 

 is interesting to remark the same peculiar contraction of the 

 cranial cavity, indicating an arrested development of brain in 

 both of them. The dental peculiarity of the African Saurian 

 forms its chief distinction from the Rhynchosaurus, as from all 

 other Sauria : but with the strange superaddition of its two 

 canine tusks, we must bear in mind that the affinities linking 



