126 BULLETIN 89, UNITED STATES NATIONAL MUSEUM. 



will be somewhat less when the plates are properly placed. The average Stegosaurus 

 would probably measure somewhat less in length, for this skeleton is based upon 

 the remains of old and very large individuals. The present weight of the fossil 

 bones is 1,917 pounds, and Lull has estimated the live weight of the animal as being 

 between 7 and 10 tons. 



As in nearly all dinosaurs the articulai' surfaces of the limb bones give but 

 httle positive evidence as to their exact manner of articulation, and any statement 

 as to their normal pose largely resolves itself into a matter of personal opinion. 



I had hoped to present at this time an illustration of a mounted skeleton of 

 Stegosaurus stenops that it is proposed to erect in the United States National Mu- 

 seum, and which would graphically portray the ideas set forth here as to the ai- 

 ticulation of the bones of the skeleton. Work of a more urgent nature, however, 

 has delayed the mounting of this skeleton and it has been deemed inadvisable 

 to longer postpone the present paper pending its completion. 



The skin covering of Stegosaurus is at this time wholly conjectural, although 

 in the Hght of recent discoveries we may yet hope to have definite knowledge as 

 to its character. Lambe^ has recently described impressions of the dermal covering 

 of a Ceratopsian as consisting of " nonimbricating plate-like and tubercle-like scales." 

 Based upon this evidence and from what is known of the integument of the Tracho- 

 dont dJnosaure it is reasonable to expect the covering of Stegosaurus to be scale- 

 like, with numerous bony skin ossicles scattered over the entire body, instead of 

 the smooth leathery elephant-like texture which has so often been represented. 



The exceedingly small and feeble teeth would appear to indicate that Stego- 

 saurus must have fed upon the most succulent of terrestrial plants. The structure 

 of the feet suggests that they were land haunting, doubtless of low swampy regions 

 rather than the upland, but they suggest the probability of being adaptations from 

 a group higlily specialized for locomotion upon land. There is every reason to 

 beUeve that Stegosaurus was descended from a bipedal ancestry as first suggested 

 by Dollo. Increasing bulk and development of the armor caused them to lose 

 celerity of movement, and they became sluggish, slow-moving creatures of low 

 mentality, only sufficient, perhaps, to direct the mere mechanical functions of life 



1 The Ottawa Naturalist, vol. 27, 1914, pp. 129-135. 



