230 Bulletin American Museum of Natural History. [Vol. XIII, 



If this or some similar phylogenetic hypothesis can be estab- 

 lished, it will not elucidate the origin, which remains an enigma, 

 but it will at once simplify the whole problem of the succession, 

 development, migration, and taxonomy of this* hitherto baffling 

 group. 



Phylogeny and Taxonomy. 



A clear conception of phylogeny is an essential preliminary to 

 taxonomy ; the nomenclature is still, as my friend Schlosser ex- 

 presses it, " ein wahres Elend"; in no European or American 

 museum are the Rhinoceroses properly identified or catalogued. 



This paper therefore, besides setting forth an hypothesis of 

 descent, is a preliminary statement of very interesting systematic 

 and comparative results obtained by visits in 1898 and 1900 to 

 the collections of London, Paris, Lyons, Munich, Darmstadt, 

 Stuttgart, Augsburg, Vienna, St. Petersburg, and Moscow. 

 Many kind friends aided in this work, especially the following 

 palaeontologists : Messrs. Lydekker, Woodward, Andrews, 

 Gaudry, Boule, Thevenin, Deperet, Filhol, Zittel, Schlosser, 

 Roger, Lepsius, Fraas, and Fritsch. The recent writings of 

 Lydekker, Pavlovv, and Roger have been of great service. 



This extended comparison was undertaken before writing 

 Part II of ' The Extinct Rhinoceroses ' memoir, because in 

 studying the American Rhinoceroses I soon learned that their 

 close relations with those of Europe rendered it necessary for me 

 thoroughly to understand the types of both countries. 



The stratigraphical or geological basis is of the utmost import- 

 ance and is set forth in recent correlation papers (Osborn, '00). 



As regards nomenclature : first, the discovery that the type 

 Acerathere, the classic Aceratherium incisivum Kaup, has a rudi- 

 mentary median frontal horn, does away with the application of 

 the generic term Aceratherium to many of the ancestral hornless 

 types ; second, valid reasons are found for reviving the discarded 

 generic terms Atelodus, Ceratorhinus, etc., and, third, the final 

 nomenclature will be an expression of phylogeny. The first 

 steps towards clearly attacking the taxonomic problem are : 



(i) To conceive of the early adaptive radiation of the Rhinoc- 

 eroses from an. unknown stem. 



(2) To conceive of the possibly independent origin of certain 



