212 EVOLUTION OF MAMMALIAN MOLAR TEETH 



cone, corresponding respective!} 7 to the para- and meta-cone as homologized 

 by Cope and Osborn. The embryogenic sequence is as follows : 



1. Protocone. 1. Protoconid. 



2. Paracone. 2. Metaconid. 



3. Metacone. 3. Paraconid. 



4. Hypoconid. 



Similarly in the young jaws of Ericuhis (op. tit., p. 574) Woodward 

 finds that in the foetal first superior molar the protocone (as homologized 

 by Cope and Osborn) " forms the main mass of the tooth, while the para- 

 and meta-cones (as homologized by Cope and Osborn) form two rounded 

 external shelves, not at present conical " ; in the second superior molar 

 " the protocone and the small antero-external paracone are alone visible." 



Summary of Woodward's Conclusions. 



Woodward (1) entirely confirms the conclusions of previous authors 

 that in the lower teeth the evidence of embryology and palaeontology 

 is identical. (2) In (I.) the quadrituberculate Insectivora he strongly 

 reinforces the previous testimony of Rose, Kukenthal, Leche and Taeker, 

 namely, that the paracone develops first and the protocone is a secondary 

 shelf. (3) In (II.) the trituberculate Insectivora, on the contrary, he 

 brings forward facts which seem to support the paheontological theory 

 and honiologies ; it is in these animals, according to the Cope-Osborn 

 theory, that the protocone is still the highest and chief cusp of the 

 crown and thus should appear first in ontogeny, while in the quadri- 

 tubercular types the protocone being more depressed and the para- and 

 meta-cone being more elevated, the earlier appearance of the latter 

 might be interpreted as due to adaptive acceleration or coenogenesis. 

 In his discussion of these facts, however, Woodward does not admit 

 this interpretation of adaptive acceleration or cienogenesis, but maintains 

 that the Cope-Osborn honiologies are incorrect, and that the main 

 internal cusp in the trituberculate group is homologous with the antero- 

 external cusp in the quadrituberculate group, as shown in the accom- 

 panying diagram (Fig. 204). More in detail, he observes: "With 

 regard to the tritubercular upper molars of the C<'nt<ti<l(c, I should 

 conclude that the main cone of this type of tooth, usually termed 

 the protocone, was really the paracone : the whole tooth representing 

 only the antero-external triangle of such a form as Talpa, i.e. the 

 crescentic paracone with its two external cingulum cusps, the last 

 named being commonly but incorrectly described as para- and meta-cone 

 in Ccntdcs: that in the Cf/tf<'/iilcc no marked indications of the protocone 

 or metacone are as yet visible, while in Chrysochloris (Fig. 36-7) the 

 first indication of the protocone has appeared, viz., the internal shelf." 



Thus he concludes as to honiologies that the reptilian cone of the 

 upper cheek teeth of the ancestral mammal is homologous with the 



