55 
jaw and inward in the upper one so that the worn surface of the teeth 
in the two jaws came together with a shearing action in an almost vertical 
direction. As a result of the curve in the vertical series, and of the over- 
lapping of individual teeth therein, as many as three or even four teeth 
belonging to a series might be in use at the same time, viz., one worn down 
to a stump, and one, two, and sometimes three succeeding teeth in pro- 
gressive stages of wear, providing a tessellated shearing surface of con- 
siderable breadth and having a length equal to that of the magazine. 
The dentary teeth succeed each other in both jaws from the inner side. 
In the dentary the enamelled face of the crown of the teeth is on the inside 
providing a continuous enamelled surface to the full extent of the maga- 
zine. The maxillary teeth bear enamel on their outer side and for this 
reason and in consequence of their inward curve the enamelled surfaces 
in the vertical series of teeth are not brought into juxtaposition after the 
manner of the mandibular teeth. 
The teeth of Edmontosaurus conform to the general rules governing 
tooth implantation and succession in the Hadrosauridse and are arranged 
in the usual closely fitting vertical rows of which there are forty-eight or 
forty-nine in the dentary with four or five teeth and sometimes the stump 
of a sixth in each row. 
The dentary teeth are largest at the mid- 
length of the magazine and decrease in size 
toward either end of it, the posterior ones 
being considerably shorter but only slightly 
narrower than those in front. The inner 
enamelled tooth-surfaces, in lateral aspect, 
are nearly lozenge-shaped in outline, with 
the longer diameter vertical, and fit closely 
together quincuncially in a mosaic which is 
almost half covered from below by the thin 
alveolar wall. The enamelled portion of the 
teeth is evenly rounded above, and emar- 
ginated at the narrow base where the apex 
of the next succeeding tooth closely fits. 
It bears a high, broad-based, sharp-edged, 
median keel running its length, between 
which and the margin on either side, the 
surface is evenly concave transversely. The 
succession of keeled teeth from below results twenty-ninth to thirty-first vertical 
• senes from the front, in left dentary 
in the whole of the inner face of the dentary of Edmontosaurus, Cat. No. 2289; na- 
magazine being regularly fluted in a ver- tural size, 
tical direction. A slight elevation of the 
margin is developed in the apical curve of the larger teeth, and is also 
present, to a varying extent, in the smaller anterior and posterior ones 
along the sides. In the majority of the dentary teeth the margins are 
smooth, but in the first five or six vertical rows marginal papillations 
occur between the tooth’s apex and the angulation at its maximum breadth. 
Three dentary teeth, of the same vertical series, in progressive stages 
of wear, are in use in the cutting surface at the same time. This number 
toward either end of the magazine is generally reduced to two. 
30 
Figure 29. Enamelled face of teeth, 
