124 G. R. Wieland — Notes on the Armored Dinosauria. 



must be the point. Though in the simple relations of attack 

 and defense involved in spines, bony plates, horns and teeth, 

 nothing we can to-day observe in the reptiles or the mammals of 

 the land or sea could have quite prepared us for that, veritable 

 apotheosis of force finally involved in the juxtaposition of 

 Tyrannosaurus with the Ceratopsia as justly included mem- 

 bers of the great group of keel-armored saurians here hypothe- 

 sized. 



Certainly then one can not bring himself to seek an explana- 

 tion of the evident parallel development of these structurally 

 antithetic series, and their brief culmination in the latest Cre- 

 taceous, as a chronological accident, explicable in terms" of 

 senility and bathmism, or of mere developmental inertia. 



That one or the other of these opposed series could so arise 

 as an aging race during continental and climatic evolution is 

 thinkable. But that both the carnivorous and horned and mail- 

 coated herbivorous Dinosaurian lines so developed their formid- 

 able array of structures of attack and defense synchronously, 

 appears improbable. Such equal rates of evolution have never 

 been demonstrated ; though in any alternative one is surely led 

 to believe that when once the Dinosaurian lines are known in 

 approximate paleontologic totality, the sequence and cause of 

 complementary development in these groups, whether simple 

 as it now seems, or obscure, may not only be largely under- 

 stood, but that the facts will aid us notably in gaining very 

 definite conceptions of fundamental biologic factors involved. 

 Indeed it is most evident that any idea that the study of the 

 Dinosauria can be in the least barren must be wholly erro- 

 neous, and that contrariwise, this group is destined to yield in 

 largesse evolutionary testimony of everyday bearing that can 

 be learned nowhere else. 



