Lull, The Armored Dinosaur Stegosaurus ungulatus etc. 57 Q 



of the crocodile. One side of the model, the left, shows the superficial 

 musculature of the body the outlines of both ileum and scapula 

 being indicated as landmarks, and also the skull and the dermal 

 plates, the latter bereft of their outer sheath of hörn. The immense 

 power of limb, neck, and especially of the tail is shown, together 

 with the slips of dermal muscle which stiffened the armor in time 

 of stress, such as are seen beneath the scutes of the alligator. The 

 right side of the modetls clothed in the skin which is indicated as 

 of a leathery, elephant-like texture with the shield of throat os- 

 sicles as well as the scattered ones over the entire frame. 



The gape of the mouth is represented as in my previous mo- 

 deis of the Ceratopsia, as extending but a short distance back, to 

 the point where the dental series begins, owing to the necessity 

 of muscular cheeks on the part of a masticating herbivorous form 

 in order to retain the food in the mouth. The gape thus includes 

 only the prehensile part of the mouth which is very small as com- 

 pared with the vast body bulk which the creature was forced to 

 sustain. 



The dimensions of the skeleton are: 



Length 5,94 m. (=19 ft. 6 in.) 



Extreme height . . „ . . . . 4,11 m. (=13 ft. 6 in.) 

 Extreme breadth across humeri. 1,20 m. (= 3 ft. 11 in.) 

 Weight of the fossil skeleton . 869.8 kilos (1917 lbs.) 

 Estimated weight when alive . (between 7 and 10 



tons) . 



VI. Conclusion. 



The genus Stegosaurus is confined exclusively to the Morri- 

 son formation, Upper Jurassic or lower Cretaceous, of Wyoming, 

 U. S. A., strata of nearly equivalent age to those of the European 

 Wealden. The character of the environment was probably similar 

 to the conception offered by Hatcher, who believed that the Mor- 

 rison beds were deposited ,,over a comparatively low and level 

 piain which was occupied by perhaps small lakes connected by 

 an interlacing System of river Channels. The climate was warm 

 and the region was overspread by luxuriant forests and broad sa- 

 vannas . . . conditions doubtless similar to those now found about 

 the mouth of the Amazon and over some of the more elevated 

 plains of western Brazil." The water areas were doubtless the 

 dwelling places of the huge contemporaneous sauropods while 

 the Stegosaurus was terrestrial and possibly frequented the forests 

 in search of the tender Vegetation upon which it browsed. It may 

 well be that the extreme relative narrowness of the animal was 

 an adaptation to forest conditions and afforded ease of passage 

 between the trunks of the tree ferns, cycads and conifers of that 

 day. Stegosaurus is rarely found entombed with sauropod dino- 



