No. 2.] THE HARD PARTS OF THE MAMMALIA. 237 
type of molar would not have come into existence in such fami- 
lies as have large canine teeth, such as the Suoid Artiodactyla. 
I do not for these reasons abandon the opinion that the develop- 
ment of the canines has not had a great deal to do with the 
development of the sectorial dentition. I only deny that it has 
been the cause of its origin; that is, of the anterior shearing of 
the lower molars on the upper, at its beginning. 
The peculiarities of the Pantodont and Dinoceratous denti- 
tion may be now taken up in order, and their mechanical causes 
assigned so far as possible. J imine I take the position that 
the mastication of the Amblypoda was accomplished by the 
transverse movement of the lower jaw across the upper, and 
that this is, therefore, the only order in which such mastication 
was preformed by the primitive dentition, z.e. the tritubercular 
and tuberculosectorial. That this is the type of mastication is 
suggested, but not proven, by the anisognathism of the dental 
system. But it is proven by the mark or path made by the pos- 
terior external cusp of the inferior true molar across the crown 
of the superior molar in the Coryphodontidz. This cusp struck 
the posterior side of the rudimental anterior external lobe, and 
passed transversely across the crown (diagonally to the principal 
cross-crests), and slid up the apex of the internal cusp, producing 
the externally di- SG {as a 
rected angle in its EEE aoe 
wear, seen in all spe- 
cimens of the gen- 
era Metalophodon, 
Coryphodon, and 
Ectacodon (Fig. 63). 
I also suspect that 
this movement is 
ectal, since the di- 
rection of the V’s of ; 
the two dental series Figure 62,— Bones and teeth of Pantolambda bath- 
modon Cope, two-thirds nat. size. From the Puerco 
beds of New Mexico. Fig. a, part of maxillary and 
An attempt at an jnalar bones from below, showing true molars, all some- 
ental movement re- what broken. Figs. 4 and ¢, cervical vertebree, left side; 
sults in a jamming WY andc, do. from below. Fig. d, astragalus from above; 
f the V’s into each d', from front, showing facet for cuboid; d_ ,from below; 
3 e, navicular bone from below. Original, from Report 
other, and further U.S, Geol, Surv, Terrs., F, V. Hayden. 
will permit no other. 
