Cope. ] 82 [Feb. 17, 
across the upper, and that this is, therefore, the only order in which such 
mastication was performed by the primitive dentition, 7. ¢., the trituber- 
cular and tuberculo-sectorial. That this is the type of mastication is sug- 
gested, but not proven, by the anisognathism of the dental system. But 
it is proven by the mark or path made by the posterior external cusp of 
the inferior true molar across the crown of the superior molar in 
the Coryphodontide. This cusp struck the posterior side of the rudi- 
mental 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 directed angle in its wear, 
seen in all specimens of the genera Metalophodon, Coryphodon and 
Ectacodon (Fig. 3). I also suspect that this movement is ectal, since the 
directions of the V’s of the two dental series will permit no other. An at- 
Fic. 1.—Bones and teeth of Pantolambda bathmodon Cope, two-thirds nat. size. From 
the Puerco beds of New Mexico. Fig. a, part of maxillary and malar bones from below, 
showing true molars, all somewhat broken. Figs. b and c, cervical yertebree, left side ; 
v/ and ¢’, do. from below. Fig. d, astragalus from above; a’, from front, showing facet 
for cuboid ; d’, from below ; é, navyicular bone from below. Original, from Report U. 8, 
Geol. Sury. Terrs., F. V. Hayden. 
tempt at an ental movement results in a jamming of the V’s into each 
other, and further progress is impossible. It may be objected that the 
presence of the large superior canines forbids any considerable lateral 
movement of the lower jaw. The superior canines are however so diver- 
gent in the Coryphodontide that such movement is possible, and the trans- 
versely convex wear of these teeth proves just such a movement of the in- 
ferior canines on them. The lateral movement in the old males of the 
Dinocerata hag been much restricted, but in younger males and females it 
was possible. 
A second proposition is demonstrated by the discovery of the Panto- 
lambdide. This is, that the superior molars of both the Coryphodontide 
and Uintatheriide are derived from a type with two external V’s (Panto- 
lambda, Fig. 1), and I propose to show how ‘this derivation has been 
sires amnion ero 
SLE et estonia ence OTN 
