450 DR. H. W. MA.EETT TIMS Olf THE 



Osborn's results as to tlie homologies o£ the molar cusps, those 

 of the premolars are differently arranged." 



In consideration of these facts, I would submit the following 

 attempt at identification : — 



To start from the upper carnassial tooth, in which there are 

 two external cusps and a very minute antero-internal cingulum- 

 cusp. Following Cope (2), the Paracone and Metacone are 

 defined as the autero- and postero-external cusps, and I think 

 it is justifiable to name the two main cones (fig. 1, pa and me) 

 o£ this tooth the Paracone and Metacone. The other very 

 minute cusp must then be the Protocone or antero-internal cusp. 

 It is remarkable that the cone representing the primitive reptilian 

 cone should be so diminutive, even allowing with Prof. Osboni 

 (13) that the Paracone and Metacone have undergone " accele- 

 rated development." 



Turning now to my own identifications in the dpin^. There is 

 a main cone with its internal cingulum, the latter structure 

 giving rise to a small antero-internal cusp and a somewhat more 

 pronounced posterior cusp lying in the same antero-posterior line 

 as the main cone. I presume that the main or antero-external 

 cone would be regarded by Professors Cope and Osboru as the 

 Paracone, the postero-external cusp, which, as we have seen, is 

 formed by the cingulum, as the Metacone, and the antero-internal 

 cingulum-cusp as the Protocone. If this be so, and I see no 

 other alternative, the Protocone is still more reduced, indeed 

 scarcely perceptible. 



In dealing with the canines and incisors there are two alter- 

 natives : — 



(i.) That there is no internal cusp, and that therefore there 

 can be no Protocone present ; or 

 (ii.) That the cusp homologous with the so-called Protocone 

 of the deciduous premolars is the small anterior 

 cingulum-cusp (fig. 1, cd). 



The latter alternative I believe to be the more probable. If 

 this be so, I think it is trespassing too much upon credulity to 

 regard this minute cingulum-cusp, and not the main central cone, 

 as the primitive cone from w^hich all the others have been 

 derived. Moreover, this cusp is formed by the cingulum, which 

 is itself regarded as a mammalian structure superadded to the 

 reptilian type of tooth ; and consequently it is a " reductio ad 



