98 R. S. Lull — Cretaceous Armored Dinosaur, 



the family of American plated dinosaurs, and was, more- 

 over, essentially the first of these remarkable reptiles to 

 be described in American literature of science. The 

 preparation of the skeleton has been an arduous task, as it 

 was sent in from the field in the form of shattered, bone- 

 containing fragments of one or more great concretions. 

 The only jDossible mode of procedure was to fit together 

 these fragments and then, after pouring plaster into 

 every bone impression in the rock where the osseous 

 tissue had been eroded away, to hew the matrix from both 

 the contained bone and the plaster continuation thereof. 

 In this way, through weeks of patient toil, the creature 

 has been revealed, and while by no means complete, will 

 enhance very materially our present knowledge of these 

 forms. Stegosaiirus, although difficult to understand, is 

 of course well known, owing to the researches of 

 Marsh, Gilmore, and the writer, but it represents an 

 aberrant side branch of the Stegosauria, and is early 

 extinct (Morrison time), while Nodosaurus and its allies 

 are in many respects more conservative and trace their 

 lineage from the Lower Jurassic Scelidosaurus to Anky- 

 losaurus of the Lance — almost the entire length of 

 recorded predentate dinosaurian history. 



Aiding in the work of preparation were F. W. Darby, 

 a preparator of high skill and long service, Edward L. 

 Troxell, associate on the research staff of the Peabody 

 Museum, and others. I am also indebted to W. D. Mat- 

 thew and Barnum Brown of the American Museum of 

 Natural History for photographs and the privilege of 

 studying the Ankylosaurus specimens collected by the 

 latter; to Charles W. Gilmore of the United States 

 National Museum for photographs and criticism ; and to 

 our lamented colleague, S. W. Williston, for the loan of 

 the type specimen of Stegopelta. Mr. Kirkham of Yale 

 aided in certain interpretations for which my knowledge 

 was insufficient, while Professor Schuchert and Miss 

 LeVene have as usual given their very real aid to the 

 undertaking. 



History of discovery,— When the veteran collector, 

 William H. Reed, was working for Professor Marsh in 

 1881, searching for mammals and reptiles in the Morrison 

 strata on the western slope of Como Bluff, Wyoming, he 

 happened to discover the dinosaur which Marsh later 

 described as Nodosaurus textilis. The specimen was 

 found about 11/2 miles east and south of the famous 



