G. R. Wieland — Notes on the Armored Dinosauria. 123 



patterns. As a rule, however, the transition from low, flat or 

 erect plates to large spines does not appear so abrupt as in the 

 case of the more or less fluted caudal spines of Stegosaurus ; 

 but taken all in all, it is evident enough that there was present 

 throughout an entire armored race a most ornate keeled anno- 

 rial pattern. And while the complexity of this pattern as yet 

 baffles exact restoration, it is now seen to be most likely that 

 forms with their armor in place will soon be discovered, reveal- 

 ing in full the structure and number of the keels, the degree of 

 earapacial and hornshield development, the extent of possible 

 comparison with the armor of the Testudinata, the correlated 

 skeletal structures, and finally following anatomical features, 

 the extent and the nature of the antithetic course of evolution 

 which must be involved in the development of the late Creta- 

 ceous carnivorous and mailed and horned Dinosauria. 



Indeed so extended has already become the evidence here 

 added to, that a further brief word of interpretation is perti- 

 nent. At first sight ail development of dermal armature may 

 appear to be mainly a senile feature, due even to inertia — the 

 general life movement of the individual and the race.* But it 

 is also evident that the development of dermal ossicles in series 

 finally resulting in a protective osteodermal armature or cara- 

 pace is a most profound change coordinated with striking endo- 

 skeletal alteration. Used with less success by the Dinosauria, 

 as already much specialized, the accomplishment of this change 

 however appears to have given the Testudinata an exceedingly 

 long lease of life. 



It is hence in our view most probable that not so much 

 bathmic courses and tendencies as ordinary exigencies of life 

 and environment were really primary factors in the origin of 

 armored reptilian races. At least ever since the discovery that 

 races of formidable carnivores like Megalosaurus and Lcelajps 

 developed side by side with such strongly armored herbivores 

 as Scelidosam'iis, Ilylceosaurus and Stegosaurus, it has seemed 

 reasonable to believe that a completer knowledge of Dino- 

 saurian faunae must finally reveal some of the modes of adjust- 

 ment to a life of attack and defense in these dominant but 

 comparatively short-lived apposite lines. For if ever the ver- 

 tebrate paleontologist might hope to detect boundaries between 

 the direct origin of organs to meet obvious necessities, and 

 their appearance with the aging of races as secondarily used 

 senile features, here where all the characters are writ large 



* On page 106 of this Journal, Aug., 1902, the parallel modification of cer- 

 vicals in long separated Testudinate races was cited by the writer as a case 

 of evolutionary inertia. It is a conspicuous one, and is correctly named 

 inertia, whereas the term momentum, now used by some, implies a knowl- 

 edge of rates of evolution we do not as yet possess. The general term is 

 certainly preferable. 



