CHAPTER IV. 



TRITUBERCULY IN ITS APPLICATION TO THE MOLAR TEETH OF 

 THE UNGULATES OR HOOFED MAMMALS. COMPLETION <>K 

 THE NOMENCLATURE. 



1. 



DISADVANTAGES OF PREVIOUS SYSTEMS OF NOMENCLATURE OF TIIH 



MOLAR CUSPS. 



[Extract from article entitled "The Nomenclature of the Mammalian Molar Cusps,'' 



The American Naturalist, October 1888.] 



IN view of the evidence for the almost universal presence of the tri- 

 tubercular stage in the present or past history of the upper and lower 

 molars, I have already advocated a distinct nomenclature for the different 

 cusps which compose this molar and its derivatives, up to the stage of the 

 acquisition of six tubercles in the upper molars and five in the lower. 

 This is the final stage in which the tubercles remain distinct. The 

 nomenclature now in general use is based, for the most part, upon the 

 secondary or acquired position, and in no instance, so far as I know, upon 

 the demonstrable homologies of the cusps in the upper and lower jaws. 

 Compare, for example, the molars of Miodcenus and Hyopsodus. By those 

 familiar with Cope's writings upon this subject, it will be recognized at 

 once that the antero-internal cusp of the lower molar of Miodcenus is not 

 homologous with the antero-internal cusp of the upper molar of the same 

 genus, nor is it homologous with the antero-internal cusp of ihe lower 

 molar of Hyopsodus. 



2. 



METHODS OF ANALYSIS OF MOLAR ELEMENTS, NOMENCLATURE OF THE 



MOLAIIS OF UNGULATES. 



[Extract from Osborn and Wortman, " Fossil Mammals of the Wahsatch and Wind 

 River Beds Collection of 1891," Bull. Ame.r. Mm., Nat. Hist., Vol. IV., No. 1, Oct. 20th, 

 1892, pp. 84-93.] 



In October, 1888, a table of nomenclature for the cusps of the molar 

 teeth of mammalia was published in the American Naturalist. } The 



1 Osborn, " The Nomenclature of the Mammalian Molar Cusps," op. cit., p. 927. 



