R. S. Lull — Stegosaurus imgulatus Marsh. 375 



musculature of the body, the outlines of both ilium and scapula 

 being indicated as landmarks and also the skull and the dermal 

 plates, the latter bereft of their outer sheath of horn. 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 I'ight side of the model is clothed in the skin, 

 which is indicated as of a leathery, elephant-like texture, with the 

 shield of throat ossicles, as well as the scattered ones over the 

 entire frame. 



The gape of the mouth is represented, as in my previous 

 models 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 her- 

 bivorous 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 compared with the vast body bulk which tlie 

 creature is forced to sustain. 



YI. Principal 3feasurements. 



Length between ^perpendiculars ]9ft. 5 in. 



" of tail between perpendiculars 8 " 8 " 



Height of sacriira 9 " 11 " 



'' highest plate - 11 " 10|- " 



" muzzle 3" 4 " , 



" tail tip 4" li " 



Width of hips 3" 5|" 



" shoulders 3 " 10^ " 



" chest 3" 8^ " 



Height of shoulder 4 " 4 " 



" elbow 2 



" hip 7" 6 



" knee 3 



1^ 



"I 



Present weight of the fossil skeleton, 1917 lbs. 

 Estimated live weight, between 7 and 10 tons. 



VII. Life Conditions and Relationships. 



The genus Stegosaurus is confined exclusively to the Morrison 

 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 Morrison beds were deposited " over a com- 

 parativel}'' low and level plain which was occupied by an inter- 

 lacing system of river channels. The climate was warm, and 

 the region was overspread by luxuriant forests and broad 



