60 MEMOIRS OP THE CARNEGIE MUSEUM 



toward the opinion that Diplodocus was essentially an aquatic animal, but quite cap- 

 able of locomotion on land. Though living for the most part in the more im- 

 portant rivers and freshwater lakes, it may not infrequently have left the water and 

 taken temporarily to the land, either in quest of food or in migration from one to 

 another of adjacent bodies of water. Not only would an aquatic life seem to har- 

 monize best with the anatomical characters of Diplodocus as we know them, but such 

 a habitat would also afford these comparatively helpless animals the greatest pos- 

 sible protection from the huge terrestrial carnivorous Dinosaurs which lived con- 

 temporaneously with them and were undoubtedly their constant enemies. 



Bearing in mind the enormous size of the animal and the great quantity of food 

 necessary for its sustenance, in consideration with the extremely small and almost 

 edentulous skull, it will readily appear how important to the existence of these 

 animals was the nature of their environments. They were remarkably ill adapted 

 for maintaining themselves amidst varying conditions. Not only was an almost in- 

 exhaustible food supply necessary to their existence, but they were also equally de- 

 pendent upon the nature of the food. • The small, pointed, imperfectly socketed 

 rake-like teeth of Diplodocus^ only present in the anterior portion of the mouth, 

 were of little or no use as masticating organs, but would have served the animal 

 very well as prehensile organs useful in detaching from the bottoms and shores the 

 tender, succulent aquatic and semi-aquatic plants that must have grown in great 

 abundance in the waters and along the shores of the Jurassic streams and lakes in 

 and about which these animals lived. It is not improbable that during the period 

 when these huge dinosaurs lived and flourished over what is now New Mexico, 

 Colorado, Wyoming, Montana, and the Dakotas there prevailed throughout this 

 region physical conditions somewhat similar to those which exist to-day in tropical 

 America and more especially over the coastal plain of the lower Amazon with its 

 numerous bayous and islands, or the more elevated valleys of the interior in the 

 Brazilian provinces of Amazonas and Matto Grosso with their numerous lakes and 

 large rivers surrounded by a dense tropical vegetation with broad, level valleys sub- 

 ject to periodical inundations. It is only in the midst of such conditions that we 

 can suppose it was possible for these animals to have existed, while comparatively 

 very limited climatic or other physical changes affecting either the abundance or 

 nature of their food supply would have rendered their existence precarious and 

 finally led to their extermination. During the late Jurassic and in early Cretaceous 

 times the western portion of the great interior basin of North America was but 

 slightly elevated, and for the most part consisted of vast morasses with occasional 

 open bodies of water connected by deep but sluggish streams. Here in the midst 



