A GREAT PERMIAN DELTA 



56i 



fierce scuttling rush out upon its prey, perhaps some slow-moving 

 reptile or amphibian, perhaps even some smaller individual of its own 

 kind, for there is ample evidence that these animals waged fierce battles 

 anion gf themselves. It is not uncommon to find bones which have 

 been broken during life and healed again, telling of furious reptilian 

 contests in the struggle for mates or for territory, or perhaps with the 

 single idea of a cannibalistic meal. 



But a more wonderful animal still has left its remains in the rocks. 

 In this form there were high spines on the back, but instead of the 

 spines being simple they were furnished with projecting processes on 

 the sides, not unlike the yard-arms of the old-fashioned sailing ships. 

 This resemblance led Cope to call the animal Naosaurus, ship-lizard. 

 In a recent restoration of Naosaurus it has been given the skull of the 

 fiercely carnivorous Dimeirodon, the general similarity of the forms 



Fig. 4. Anterior Portion of the Jaw of Dimctrodon, showing the great tusks. 



seemed to warrant this, but recent discoveries have made it probable 

 that Naosaurus was not an eater of flesh, but a peaceful, sluggish 

 eater of shell fish and perhaps of vegetation. This animal has perhaps 

 the most wonderful dentition of any known animal the incisor teeth 

 are sharp and chisel-shaped, such as might be useful in cutting strong 

 vegetation; behind these are five sharp triangular cutting teeth, not 

 unlike the sectorial teeth of such flesh eaters as the tiger and lion; 

 behind these are simple cones, such as would be useful in holding a 

 struggling victim. But most wonderful of all, on the palate and in a 

 corresponding position on the lower jaw were heavy plates of bone, 

 covered by short stumpy teeth, such as occur in the jaws of fish which 

 live upon molluscs. The animal was seemingly omnivorous, but in- 

 stead of having a dentition of a generalized pattern like that of the 

 pig or the human being, there was a set for each kind of diet. The 



VOL. LXXIII. — 36. 



