.26 BULLETIN 89, UNITED STATES NATIONAL MUSEUM. 



OSTEOLOGY OF STEGOSAURUS. 



In the pages that follow is given, for the first time, a detailed account of the 

 complete skeletal anatomy of Stegosaurus. These descriptions are based entirely 

 upon specimens belonging to the vertebrate paleontological collections of the United 

 States National Museum, and primarily upon the very complete skeleton, briefly 

 described 1 by Marsh as the type of the species S. stenops. (Cat. No. 4934.) I have 

 selected this specimen on account of its comprising a considerable part of one indi- 

 vidual, and from the fact that most of the bones were found articulated, or at least 

 so little disturbed, that there can be no question raised as to their proper association. 

 Where important structural differences exist, reference is made to other individuals, 

 and bones not represented in this specimen or not sufficiently preserved to show 

 their more important characteristics are described from other specimens. 



Skull. 

 Plates 5, 6, 7, 8, 9, and 10. 



The cranium belonging to the type of Stegosaurus stenops is unique as being the 

 most perfect skull of the genus yet discovered, and although slightly distorted from 

 pressure, it is otherwise most perfectly preserved, as is well shown in plate 19, 

 fig. 1 , reproduced from a photograph of the specimen. 



In the National Museum collections are five other cranii, in varying degrees 

 of preservation. Two of these are to a great extent disarticulated. These, however, 

 are of especial value in the proper interpretation of the elements in the articulated 

 skulls, and they also make possible a more detailed description of the separate bones 

 of the skull than could otherwise be given. 



Summary of cranial materials. — The cranii in the United States National Museum 

 are as follows : 



1. Stegosaurus stenops. Complete skull and jaws from Quarry No. 1, Canon 



City, Colorado. Collected by M. P. Felch, 1886. Mounted with skeleton 

 No. 4934. Sectioned. 



2. Stegosaurus sp. Disarticulated skull and portions of lower jaw. No. 4935, 



from Quarry 13, diagram 4, Como, Albany County, Wyoming. Collected 

 by Fred Brown, 1884. 



3. Stegosaurus stenops. Occiput and brain case, with a few other elements. 



No. 6645, from Quarry 13, diagram 13, Como, Albany County, Wyoming. 

 Collected by Fred Brown, 1887. 



4. Stegosaurus sp. Fragmentary skull and portions of lower jaw. No. 7637, 



from Quarries 13 East and 13 Middle, Como, Albany County, Wyoming. 

 Collected by W. H. Reed, 1882. 



5. Stegosaurus armatus Marsh. Posterior half of skull. No. 4936, Quarry No. 1, 



Canon City, Colorado. Collected by M. P. Felch, 1884. Sectioned. 



6. Stegosaurus stenops ? Posterior portion of skull. No. 2274, Quarry 13, diagram 



5, Como, Albany County, Wyoming. Collected by Fred Brown, 1885. 



i Amer. Jour. Sci., ser. 3, vol. 34, 1SS7, p. 414. 



