442 PROCEEDINGS OF THE ACADEMY OF [1892. 



cusps, which in the latter are all of nearly equal size. This inter- 

 pretation confirms Riitimeyer's view that cl* in the artiodactyls rep- 

 resents a molar with a pair of cusps added to it in front and that 

 the posterior pair do not correspond to the talon of m^. 



So far as they go, therefore, the facts of palaeontology indicate 

 that in the milk teeth the homologies of the cusps agree with those 

 of the premolars rather than those of the molars. 



The foregoing paper had been nearly completed before I received 

 the valuable and interesting articles of Taeker (No. 12) and Rose 

 (No. 8), in which the problem of the homologies of the molar and 

 premolar cusps is investigated from the embryological standpoint. 

 Taeker has confined his attention to the milk molars and finds that 

 the homologies of the cusps in these teeth agree with those of the 

 permanent premolars, so far as these homologies are determined by 

 position. Taeker had not seen my notes on the premolars and 

 attempts to horaologize the milk teeth cusps with those of the true 

 molars, but with the result that the paracone is always the first ele- 

 ment to appear. I have shown that this element is really the pro- 

 tocone and consequently the palpeontological and embryological 

 results are in exact accord. Further, Taeker shows that the order 

 of succession of the cusps in dj in the recent artiodactyls is the 

 same as we have found it to be in the Oreodontidce, viz. : proto-, 

 trito-, tetarto- and deuterocones. Again there is an exact correspon- 

 dence in the results as to the characteristic d* of the artiodactyls, 

 except that Taeker gives the name of paraconid to both of the 

 anterior cusps. Needless to say, this cannot be correct, though it is 

 not worth while to coin a special term for the antero-internal cusjd. 



Rose's investigation brings out the very unexpected fact that in 

 their embryological development the true molars agree with the pre- 

 molars and the milk teeth, and that in them also the first element 

 to appear is the antero-external cusp, which in the upper molars has 

 hitherto been considered the paracone, but which Rose believes to 

 be the protocone. The evidence offered is not altogether conclusive 

 and is open to a different explanation, but should Rose's view prove 

 to be correct, it would follow that the molar and premolar cusps are 

 really homologous after all, and the nomenclature which I have 

 proposed for the latter would be suj^erfluous, while the names now 



