180 DINOSAURS OF NORTH AMERICA. 



forms from the two countries. Portions of one Wealclen animal, refer- 

 red by Mantell to Pelorosauxus, are certainly very similar to some of 

 tbe smaller forms of Morosaurus, especially in the proportions of the 

 fore limbs, which are unusually short. This fact would distinguish 

 tljem at once from Pelorosaurus, and until the skull and more of the 

 skeleton are known they can not be separated from Morosaurus. 



The only Sauropoda reported from other parts of the world are some 

 fragmentary remains from India, referred by Lydekker to the genus 

 Titanosaurus, and more recently other remains from Madagascar, which 

 the same author has placed in the genus Bothriospondylus. The wide 

 distribution of the forms already known indicates that many future dis- 

 coveries may be expected. 



» 



PREDENTATA. 



The third order of the Dinosauria, according to the system of classi- 

 fication here adopted, is the one named by the writer the Predentata, 

 a name derived from the fact that all the members of the group have a 

 predentary bone, which is wanting in all other dinosaurs, and in fact 

 in all other vertebrates, living and extinct. This order includes three 

 suborders: the Stegosauria (plated lizards), the Ceratopsia (horned liz- 

 ards), and the Ornithopoda (bird-footed). These are all herbivorous 

 forms, and most of them contain species of very large size. The Steg- 

 osauria were mainly confined to the Jurassic, the Ceratopsia entirely to 

 the Cretaceous, while the Ornithopoda were abundant in each of these 

 periods. Of the Jurassic forms the Stegosauria will be first discussed, 

 especially the typical family Stegosauridae, which contains the Ameri- 

 can forms. 



STEGOSAURIDM. 



The genus Stegosaurus, the type of the family, was described by the 

 writer in 1S77 from a specimen found in the Atlantosaurus beds of Colo- 

 rado. Subsequently other remains were discovered and described by 

 the writer, the more important being from near Lake Como, Wyo., and 

 Canyon, Colo., localities which have furnished so mauy type specimens 

 of the Sauropoda and other dinosaurs. 



STEGOSAURUS. 

 THE SKULL. 



The skull of Stegosaurus is long and slender, the facial portion being 

 especially produced. Seen from the side, with the lower jaw in posi- 

 tion, it is wedge-shaped, with the point formed by the premaxillary, 

 which projects well beyond the mandible, as shown in fig. 1, PI. XLIII. 

 The anterior nares are large and situated far in front. The orbit is 

 very large and placed well back. The lower temporal fossa is some- 

 what smaller. All these openings are oval in outline and are on a line 



