1896.] MAMMALIAN DENTITION. 589 
or metacone are as yet visible, while in Chrysochloris (fig. 36.7) the 
first indication of the protocone has appeared, viz. the internal shelf. 
This attempt to homologize the main cone of the upper molars 
of the Centetide and Chrysochloris with the paracone of other 
Insectivora is a modification of the view put forward by Mivart in 
1868 (12). He regarded the tricuspid triangular crown of the 
molar teeth of Centetes as a concentration of the eight cusped teeth 
of Talpa. An examination of his figures and description will show 
that he believed the so-called paracone and metacone of Centetes and 
Chrysochloris to be external cingulum cusps, the main cone of these 
teeth being formed by a fusion of cones corresponding to the para- 
and metacones of Tulpa, while the protocone and hypocone of the 
latter he regards as represented by the small internal lobe seen in 
Chrysochloris*. This view accords in its most important respects 
with mine, but I do not think that the ontogeny of the tritubereu- 
late insectivore molar justifies Mivart’s fusion theory, but rather 
suggests that this tooth corresponds only with the paracone 
triangle of the Mole’s tooth. 
Such aa interpretation would bring these forms into entire accord 
with the other Insectivores and the Mammalia in general, and we 
should then find that the cusp which directly continues the dental 
germ, and consequently is the first to develop, is in all cases homo- 
logous, though unfortunately the same name has not been applied 
to it in all cases. 
Thus the primitive cone of the upper cheek-teeth of the ancestral 
mammal finds its homologue in the protocone of the premolar, in 
the paracone of most molars, but in the protocone of the molars of 
the trituberculate Insectivores and Peralestes. This has been proved 
ontogenetically for both the premolars and molars, phylogenetically 
also in the former, while in the latter the phylogeny of the 
primitive cusp is still doubtful. 
The evolution of the primary cusp of the premolars and molars 
is now brought into harmony, and it is no longer necessary to 
suppose that the cusp arrangement of two teeth such as pm. 4 and 
m. 1, often identical in pattern, have evolved upon different lines. 
To briefly recapitulate my conclusions :— 
(1) The antero-external cone, or paracone above and proto- 
conid below, is the primitive cone both in the molars and 
premolars. 
(2) The protocone is borne on an internal shelf of secondary 
origin (internal cingulum). 
(3) The metacone is a similar backward development of the 
paracone, arising very early long before the protocone. 
(4) The hypocone stands related to the metacone as the 
protocone does to the paracone. 
(5) The paracone as the primary cone in the upper molars 
finds its homologue in the protoconid below *. 
1 Unfortunately the cones have been incorrectly lettered in his figure of the 
upper molar of Chrysochloris, as may he seen on reference to his description. 
2 A paper by Winge (26) in Danish evidently upholds the same view, viz., 
that the paracone is the homologue of the protoconid; unfortunately I am 
unable to read the paper, but his lettering in his plate and diagrams are very 
clear on this point. 
