12 i?. S. Lull — Dinosaurian Distribution. 



of defence as well as a remarkable body armament of huge 

 probably upstanding plates, became too highly specialized to 

 survive and apparently died out early in the Lower Cretaceous. 

 Its allies, however, still lived on until the close of the Mesozoic, 

 developing over the rear of the body in Polacanthus of the 

 English AVealden, and later in Ankylosaurus of the Laramie, 

 a veritable cuirass, glyptodon-like in its perfection, covering 

 what seemed to be the most vulnerable portion of the body. 



That the Ceratopsia were aggressive fighters among them- 

 selves, as the cattle are to-day, is known from the frequent 

 punctures of skull and frill, broken horn-cores, and such san- 

 guinary evidences. That they held their own against the ter- 

 rible carnivores of their time is shown by their survival until 

 the close of dinosaurian history. 



The environment of the Cretaceous Orthopod dinosaurs and 

 of the attendant carnivores is described by Stanton (1909, pp. 

 280-282) as consisting of great areas but slightly elevated 

 above the level of the sea and occasionally actually beneath it, 

 wherein are found fresh-water, brackish water, or marine 

 deposits. Upon these great marshes vegetation became estab- 

 lished, and land animals, and those of the streams and lagoons 

 as well as the bays and estuaries, sought their appropriate 

 habitats. 



In speaking of the conditions prevailing toward the close of 

 the Cretaceous, Hatcher (1893, p. 14:2 ; Hatcher, Marsh, Lull 

 19*07, p. 194) says : " The Ceratops beds are thought to afford 

 evidence in themselves of having been deposited not in a great 

 open lake, but in a vast swamp with occasional stretches of 

 open waters, the whole presenting an appearance similar to 

 that which now exists in the interior of the Everglades of 

 Florida. This condition would account for the frequent 

 changes from one material to another in the same horizon.* * * 



" The conditions that prevailed over this region during the 

 period in which the Ceratops beds were deposited were prob- 

 ably those of a great swamp with numerous small open bodies 

 of water connected by a network of water courses constantly 

 changing their channels. The intervening spaces were but 

 slightly elevated above the water level or at times submerged. 

 The entire region where the waters were not too deep was 

 covered by an abundant vegetation, and inhabited by the huge 

 dinosaurs (Triceratops, Torosau?ms, Glaosaurus, etc.), as well 

 as by the smaller crocodiles and turtles and the diminutive 

 mammals, all of whose remains are now found embedded in 

 the deposits." 



For the terrestrial Orthopoda, such as Camptosaurus and 

 Iguanodon, the cycads and ferns which grew in such profusion 

 during their time would supply ample nourishment. Stegosau- 



