588 MR. M. F, WOODWARD ON [May 5, 
cingulum seen in Peralestes is comparable with the similar structure 
so frequently present in this group, and well exemplified in the 
upper molars of Zalpa. If so, it becomes further evident that the 
two larger cusps of Peralestes represent the paracone and metacone 
of these living forms, these cusps being commonly developed quite 
a long distance from the external border of the tooth (Zalpa, fig. 
35). Consequently the internal shelf, which we have seen in living 
Insectivores bearing the proto- and hypocone, is not developed in 
upper molars of Peralestes. 
If this comparison is correct, we are justified in concluding that 
the upper molars of this fossil form were not tritubercular in 
the sense understood by the supporters of the Cope-Osborn theory, 
and, further, those of Kurtodon being undoubtedly ridged and 
not tuberculate, while those of Dryolestes and Diplocynodon 
are either undescribed or possess 5 cusps, we consequently have 
no paleontological evidence to support the assumption that a 
tritubercular stage was passed through by the mammalian upper 
molar in its evolutions from a protodont or possibly a triconodont 
tooth. Under these circumstances I see no reason to believe that 
the primitive cone must necessarily occupy an antero-internal 
position such as Osborn’s protocone does. 
Paleontological evidence being then wanting or so fragmentary, 
we are obliged to fall back on the less torn pages of ontogeny. 
On doing so, we find that the upper molar cusp, which develops 
first and asa direct continuation of the dental germ in the majority 
of the Mammalia, is the antero-external or paracone: this I think 
is strongly in favour of the view put forward by Rose (19), 
that the paracone is the most primitive cusp, though I think it 
would be rather confusing to apply Osborn’s term “ protocone ” to 
it, seeing that this term has been already applied to another cusp 
in the same tooth. 
Of the primitive nature of the paracone we have slight paleon- 
tological evidence if, as I have suggested, the largest cone of the 
Peralestes upper molar (Osborn’s protocone) is the homologue of the 
paracone of living Insectivores. But if we further include the 
molariform premolars in our study, we find this view is supported 
both by ontogenists (22) and paleontologists, for Scott (21 a) has 
proved, and Osborn and Wortman (32) have accepted his con- 
clusions, that the antero-external cone in these teeth is the 
primitive one from a paleontological standpoint, and Taeker has 
shown in the Ungulates, and I myself in the Insectivora, that this 
antero-external cone in the premolars develops first in the onto- 
geny of the premolar cusps. 
With regard to the tritubercular upper molars of the Centetide 
&e. (fig. 34, « & b), 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 aform as Valpa (fig. 35, a & b), 7. e. the erescentic paracone with 
its two external cingulum cusps, the two last named being commonly 
but incorrectly described as the para- and meta-cone in Centetes : 
that in the Centetide no marked indications of the protocone 
