498 GEOLOGY OF THE DENVEE BASIN. 



The type species of the present genus, Morosaurus grandis, was about 

 40 feet in length when alive. Morosaurus agilis, found near Canyon, was 

 much smaller. The genus < iamarasaurus Cope, which includes some of the 

 gigantic forms of the Sauropoda, was apparently a form nearly allied to 

 Morosaurus. and perhaps belonged to the same family. 



STEGOSAURUS. 



Although the Sauropoda are l>v far the most abundant dinosaurs in 

 this horizon, there arc other large herbivorous forms well represented, and 

 among these the Stegosauria arc the most remarkable. The type genus, 

 Stegosaurus, described by the writer in 1877, is now well known, and is 

 represented by several species, two of which, at least, occur in the Denver 

 region, where the type was found. West of the mountains, especially in 

 the Wyoming Basin, remains of this genus are also numerous in the Atlan- 

 tosaurus beds. One species from that region, Stegosaurus ungulatus, is 

 restored on PI. XXII. This figure will indicate the general form and 

 appearance of all the species of the genus, although they differ much in 

 minor details. 



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

 especially produced. Seen from the side, with the lower jaw in position, it 

 is wedge-shaped, with the point formed by the premaxillary, which projects 

 well beyond the mandible, as shown in tig. 52. The anterior nares are 

 large and situated far in front. The orbit is very huge and placed well 

 back. The lower temporal fossa is somewhat smaller. All these openings 

 are oval in outline and are on a line nearly parallel with the top of the 

 skull. In this view the lower jaw covers the teeth entirely. A single tooth 

 is shown below, in fig. 53. 



The brain of this reptile was much elongated, and its most striking 

 features were the large size of the optic lobes ami the small cerebral hemi- 

 spheres. The latter had a transverse diameter only slightly in excess of the 

 medulla. The cerebellum was quite small, due optic nerve corresponded 

 in size with the optic lobes. The olfactory lobes were of large size. A 

 cast of the brain is shown in fig 54, on the opposite page. 



In Stegosaurus the brain was one of the smallest known in any land 

 vertebrate, living or extinct. A still more remarkable feature, however, is 



