OSTEOLOGY OF THE ARMORED DINOSAURIA IN THE UNITED STATES 

 NATIONAL MUSEUM, WITH SPECIAL REFERENCE TO THE GENUS 

 STEGOSAURUS. 



By Charles Whitney Gilmore, 



Assistant Curator of Fossil Reptiles, United States National Museum,. 



INTRODUCTION. 



In 1877 Prof. O. C. Marsh described the first Stegosaurian fossils found on this 

 continent. In a series of short papers appearing at irregular intervals up to the 

 year 1897, he presented the more important facts relating to the osteological struc- 

 ture and the relationships of the genus Stegosaurus. 



Of more recent years the principal contributions to our knowledge of this 

 dinosaur have been through the work of Dr. F. A. Lucas, director of the American 

 Museum of Natural History, but formerly of the United States National Museum, 

 and Prof. R. S. Lull, of Yale University. 



In the present paper it is proposed to give for the first time a detailed account 

 of the osteological structure of Stegosaurus, to be followed by systematic descrip- 

 tions of all the type-specimens of that genus and other armored dinosaur remains 

 contained in the United States National Museum collections. With one excep- 

 tion the present work is based entirely upon National Museum material, the 

 exception being a specimen generously loaned me several years ago by Mr. W. H. 

 Reed, of the University of Wyoming, and here described as the type of a new species. 



The collections in the United States National Museum were secured largely 

 through the United States Geological Survey, which financed the explorations so 

 energetic ally carried on by field parties under the direction of the late Prof. Othniel 

 Charles Marsh. 



The material at hand includes the remains of several individuals, each of winch 

 represents a considerable part of the skeleton; also a vast number of separate bones. 

 Of the associated skeletons the type of Stegosaurus stenops Marsh is worthy of 

 especial mention, since it represents the most perfect specimen of the genus yet 

 discovered and the only one known that gives positive evidence as to the arrange- 

 ment of the dermal armor. As contributing to our knowledge of the Stegosauria 

 it ranks with the mummified carcass of Trachodon of more recent discovery and 

 exploitation. 1 



When the Marsh collection was received at the National Museum in 1S98 and 1899 

 a very small part of the Stegosaurian material was in condition for study. The 

 preparation of this material was begun in 1906 and has continued, barring some 

 interruptions, up to the close of the year 1913. All of the known Stegosaurus 



1 H. F. Osbnrn, Memoirs Amer. Mus. Nat. Hist., new ser., vol. 1, pt 2, 1912, pp. 33-54. 



