n8 EXTINCT MONSTERS 



forms as Eryops (Fig. 20), Empedias, and Dimetrodon. As these 

 are not completely known, we have refrained from attempting 

 to restore them. Perhaps the most remarkable is the Dimetrodon l 

 (see Fig. 33) belonging to the order Pelycosauria. Not only 

 was the skull provided with formidable tusks, but the vertebrae 

 of the back present a new feature in having very long neural 

 spines. In one species the height of the spine is actually more 

 than twenty times the length of the centrum! According to 

 Professor Cope, these spines formed a kind of elevated fin on the 

 back, of which it is difficult to imagine the use ; but then there 

 are many living animals with bony structures which, if only 

 known in a fossil state, would greatly puzzle every one. 

 Plate XIII. shows a photograph of a restoration of the allied 

 Naosaurus from Permian strata of Texas, for which the writer 

 is indebted to Professor H. F. Osborn. We will take Protero- 

 saurus next. 



The skull is more lizard-like than crocodilian. There are 

 mainly two interpretations of this fossil. (1) Cuvier and Huxley 

 class it unreservedly with the lizards. (2) Von Meyer and Owen 

 consider that it represents a new type of reptile. Von Meyer 

 published an elaborate monograph on the subject, with nine folio 

 plates (1856). Professor Seeley also considers that it shows no 

 particular affinity with any living group of reptiles. It evidently 

 came of a very ancient stock. With regard to its habits, Owen 

 concluded that it was an aquatic animal. He says, " The strength 

 of its neck and head, and the sharpness of its teeth, enabled it to 

 seize and overcome the struggles of the active fishes of the waters 

 which deposited the old Thuringian copper-slates." There can be 

 but little doubt, however, that it was capable of walking on land 

 as well as of disporting itself in the water Certain ganoid fishes 



1 Greek dis, double ; metron, measure ; odous, tooth. 



