XXX AUTHOR'S PREFACE. 



Lucas, of the United States National Museum, I am indebted for many courtesies and for the 

 free use of the large collections of horned dinosaurs belonging to that institution, second only 

 in importance to the collections in the museum of Yale University. To the Canadian 

 Geological Survey I am under obligations for the original drawings and electrotypes used in the 

 illustrations accompanying the memoir by Prof. H. F. Osborn and Mr. L. M. Lambe, entitled 

 "On Vertebrata of the mid-Cretaceous of the Northwest Territory," published as Part II of 

 Volume III of Contributions to Canadian Paleontology of the Canadian Geological Survey. 

 My studies of the collections of the Canadian Survey have been greatly facilitated by Mr. 

 Lambe. To Professor Osborn, of the American Museum of Natural History, New York, I am 

 under obligations for the privilege of studying the collections brought together by the late 

 Professor Cope, which, notwithstanding their fragmentary nature, are of much interest in that 

 they contain a number of types, pertaining more especially to earlier and more primitive forms 

 collected by Professor Cope and his assistants in the Judith River beds of northern Montana. 



To the patience and skill of Mr. Sydney Prentice is largely due the excellent series of pen- 

 and-ink figures which accompany and illustrate the text and which set forth with clearness 

 and detail most of the more important cranial and other features, the determination of which 

 is made possible by the large and splendid collection of skulls brought together by the late 

 Professor Marsh and now in the museum of Yale University. 



I am indebted to Messrs. C. W. Gilmore, Hugh Gibb, T. A. Bostwick, A. W. Yankirk, 

 and Normann Boss for assistance in preparing certain portions of the material in the Yale 

 and National museums for study. 



Above all, however, for whatever of merit there is in the present volume science is mainly 

 indebted to that Nestor of American vertebrate paleontology, the late Prof. Othniel Charles 

 Marsh, whose generosity to a large extent made it possible to bring together the collections upon 

 which the volume is based. Nor did his contributions to the subject end here, for, as appears 

 on the title-page, the present memoir is based on his preliminary studies, and although he left 

 no manuscript aside from his published papers on the Ceratopsia he provided a fund of infor- 

 mation in the nature of finished and unfinished drawings, as well as symbols and letters on 

 specimens indicating the character and relations of different parts of the skeleton as he had 

 determined them. These have been of the greatest service, and it is a pleasure to accord the 

 fullest acknowledgment therefor. 



The more important collections belonging to the Yale University Museum and the United 

 States National Museum, upon which this volume is chiefly based, were for the most part 

 collected by me, and their value was fully recognized and appreciated by Professor Marsh, as 

 will readily appear from an examination of almost any of his publications. Yet I feel impelled 

 by a sense of justice to give recognition also to others who, as companions or assistants, shared 

 with me throughout at least a portion of the four years spent in bringing together this collec- 

 tion the hardships and vicissitudes of camp life, and who are therefore equally deserving of 

 whatever credit may be due for the accomplishment of that portion of the work. Among 

 these I would mention the late Dr. C. E. Beecher, Messrs. O. A. Peterson, W. H. Utterback, 

 A. L. Sullins, and W. H. Burwell as being especially worthy of recognition. 



The lithographic plates were executed by the late Mr. E. Crisand from drawings by Mr. 

 Frederick Berger, also deceased. Both of these gentlemen served Professor Marsh for many 

 years, the former as lithographer and the latter as delineator, materially increasing the value 

 of his publications by their skill and patience. The pencil drawings in the plates and text 

 are also by Mr. Berger. Most of the more important of the pen-and-ink drawings in the text 

 and plates are by Mr. Sydney Prentice; a few, however, representing material now in the 

 American Museum of Natural History in New York, are by Mr. Rudolph Weber, the well- 

 known artist of that institution. Wherever drawings have been reproduced from previous 

 publications full credit is given in the text and plates. 



As preparators employed upon this material under the direction of Professor Marsh, 

 Messrs. Adam Hermann and Hugh Gibb rendered especially valuable service. 



John B. Hatcher. 



