PREFACE. 



in an}' year, the additional papers are indicated by the letters 

 A A. IW, etc. Thus we have "Cope, E. D., 1884 JJ." It must be 

 understood that it is not here implied that the papers of any author 

 in any year have been issued in the order in which they follow each 

 other iri this bibliography. In the case of an author who, like Pro- 

 fessor Cope, was publishing numerous memoirs, papers, and notes in 

 many journals and Government publications, it is manifestly almost 

 impossible to ascertain the exact order of issue. If any student 

 should be under the necessity of determining such order, he will have 

 to address himself to the task. 



How successful the writer has been in collecting a complete list of 

 species only practical use of the book will prove. What has been 

 spoken of above as a list of the known species is, however, far more, 

 for under each species each genus and each group of higher rank 

 represented by any North American fossil species there has been 

 included references to the literature appertaining to it that is, to 

 put it in another way, each paper and memoir and book cited in the 

 bibliographical portion has been examined, and the proper citations of 

 it have been recorded under the species, genera, etc. , of the catalogue 

 of species. An estimate has shown that there are over 40,000 citations 

 recorded. Nevertheless, it is not improbable that some important 

 things have escaped attention. 



In the catalogue the writer has not usually cited directly the place 

 of publication of authors' papers, but has referred to them as notated 

 in the bibliography. If, to give an illustration, the student rinds 

 under Ceratops the citation, "Marsh, O. C., 1888 C, p. 477," he must 

 turn to the list of Professor Marsh's papers for the year 1888 and 

 run down the list to the letter C. He will find there the complete 

 title of that paper, place of publication, etc. This method of citation 

 has been adopted for the following reasons: (1) To economize labor 

 in the preparation of this book. The writer does not feel that it 

 could ever have been completed had he been compelled to cite the 

 journal and volume according to the usual method for all of the approx- 

 imately 40,000 references herein contained. (2) To bring the size of 

 this bulletin within limits convenient for use. To refer to papers 

 in the usual way, even with intelligible abbreviations, would have 

 increased the size of this volume probably 50 per cent or more. 

 (3) Because the writer believes that, on the whole, the method here 

 employed will save the time of the student. If the place of publica- 

 tion alone is given, no clue whatever is afforded to the nature of the 

 paper. It may or may not contain something of value to him. In 

 this bulletin he has the complete title. If he is studying the dentition 

 of a fossil vertebrate, and the paper which he rinds cited deals with 

 the vertebrae, or the carpus, or the habits of the animal in question, he 

 needs to go no further. The time saved in making one trip to a 



