io8 



EXTINCT MONSTERS 



Some of the arguments used by Owen in his Memoir, above 

 referred to, may be briefly condensed as follows : The creatures 

 to which these skulls belonged were not mammals (although to 

 an evolutionist they are a foreshadowing of that class), both on 

 account of the double nasal apertures, one of which is seen in 

 Fig. 26; and also because no mammal has a brain-cavity so 

 relatively small. They were not crocodiles, as indicated by 

 certain other features of the skull. They were not turtles or 



FIG. 26. Anomodont skulls. A, skull of Dicynodon ; B, skull of Oudenodon, 

 from Karoo strata, South Africa. (After Owen.) 



tortoises, for all such reptiles have a single nasal opening placed 

 in the middle of the fore part of the skull. They could not be 

 fishes, for fishes breathe in quite a different way. Neither could 

 they be batrachians (frogs, etc.), nor yet snakes, as is also proved 

 by the structure of their skulls. Certain other features of the 

 skull show a relationship with the Lacertilians, or true lizards. 

 The skulls are mostly of small size ; but that of Dicynodon 

 tigriceps is as much as twenty inches in length. That of 



