472 DE. H. W. MABET I TIMS ON THE 



It may be as well to summarize the arguments "which may 

 he now urged against the Tritubercular theory : — 



(i.) That in not one of the four orders, Marsupials, Ungulates, 

 Carnivora, or Primates, does the Profcocone develop first. 



(ii.) That in two out of the four orders it does not even develop 

 second, being preceded by the Metacone. 



(iii.) The frequent absence of the Paracouid. 



(iv.) That in the Marsupials the Metaconid, which, together 

 with the Paraconid, is second in importance only to the Proto- 

 conid, is developmentally preceded by the Hypoconid and 

 Entoconid. 



(v.) That if the homology of the cusps which I have already 

 attempted to give be correct, it follows that the Protocone is 

 absent from all the teeth of the Canidse, and, I think it may be 

 added, from all the teeth of the Carnivora, with the exception of 

 the true molars, 



(vi.) That the Protocone is absent from the molariform dpm.^ 

 of the Dog, a tooth of exceediugly primitive characters. 



(vii.) The absence of the Protocone from the "^ of such a 

 form as Cyon rutilans, this tooth, as I have already pointed out, 

 having characters very similar to dpm.^ of the Dog. 



(viii.) The absence of any evidence of the commencement of 

 the movement of rotation of the cusps, such as is presumed to 

 have taken place; and 



(ix.) The existence of the Multituberculata at such an early 

 geological period. 



In addition to these, several very weighty objections have been 

 forcibly urged by Dr. Porsyth Major in his paper on the Miocene 

 Squirrels (11). 



Another theory to account for the tooth-genesis of the Mam- 

 malia is that which was advanced by Forsyth Major (11), and 

 supported by Goodrich (5) and others, and is known as the 

 Multitubercular theory. 



These authors would derive all teeth from the Multituberculata 

 type ; but I think there are strong objections to this view also, 

 for the following reasons: — 



(i.) This view does not attach any special importance to any 

 one cusp over another ; and yet we find that the antero-external 

 cusp always develops first both in the upper and lower jaws, 

 the other cusps being added subsequently in a more or less 



