CHAPTER IV. 



SYSTEMATIC DESCRIPTIONS OF GENERA AND SPECIES. 



METHOD OF TREATMENT. 



In the following systematic descriptions all the various genera and species that have at any 

 time been referred to the Ceratopsia will be included, and all specimens that have ever been 

 used either as types of new genera and species or as pertaining to hitherto unknown portions of 

 forms previously described will likewise be included, regardless of the present author's opinion 

 relative to the synonymy of the various generic and specific names or of the correct identifica- 

 tion or reference of any of the elements that have at various times been described by different 

 authorities from materials found in such isolated position as to render their correct reference 

 uncertain or largely, at least, a matter of individual opinion. In all such instances the original 

 descriptions and figures of the various authors will first be given in full, even at the risk of 

 tediousness, and will be followed by a presentation of the present author's views. 



In the diagnoses and descriptions of the various genera and species a reference will first be 

 given to the original description of each. This will be followed by references to all later publi- 

 cations by the original author in which a further elucidation of the characters of the genus or 

 species under consideration may have been undertaken, based either on the subsequent discovery 

 of new and more perfect material or on a more complete description of the original type. A 

 reference will also be made to the more important literature by other authors. 



In the treatment of each genus and species, when possible, the parts forming the original 

 type will be listed and definitely located, and the name of the museum to which each now 

 belongs will be given, as well as the distinctive numbers which have been assigned to them in 

 such museums, so that in each instance a permanent record may be available as to the character 

 and location of all types which have served as the basis for new genera or species. 



In the descriptions of genera and species the original description of each will be given 

 verbatim. This will be followed by such additional extracts from subsequent publications, 

 either by the founder of the genus or species under discussion or by other authorities, as shall 

 appear to the present author to be important. All original descriptions of type specimens will 

 be given as quotations and all types accessible to the present author will be carefully figured 

 regardless of his opinion as to synonymy, the aim being to put the reader in possession of all the 

 facts upon which the opinions of the present and all previous contributors have been based, so 

 that each student may be able intelligently to arrive at his own conclusions wherever differences 

 of opinion may exist. 



While the distinctive characters of the various genera and species must of necessity be very 

 largely based on the original types, yet wherever a genus or species is accepted as valid no oppor- 

 tunity will be omitted further to elucidate its characters by the introduction and description of 

 such additional material as may appear to the writer to be referable to the same, care always 

 being taken, however, to state distinctly that such material does not pertain to the type and 

 definitely to locate it by its appropriate number and a reference to that museum to which it 

 belongs. 



Although the very large collections brought together by the late Prof. Othniel Charles 

 Marsh will serve as the basis of the present volume, free use will also be made of the material 

 collected by the late Prof. Edward Drinker Cope, as well as of that brought together by the 

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