40 
The length of the right mandibular ramus of Edmontosaurus (specimen 
Cat. No. 2289) is 910 mm. 
Dentary. (Dn.). Figures 3, 4, 20, and 21. This element is large 
with three-eighths of its length in front edentulous. It is deeply excavated 
posteriorly by the mandibular fossa and the dental magazine occupies 
nearly one-half the length of the bone. The coronoid process is 
robust and placed far back, and gives to the dentary its maximum 
breadth. For the full length of the magazine the bone is deep and moder- 
ately thick. The edentulous part is comparatively thin, with a gradually 
lessening depth forward, and longitudinally concave internally. It 
curves abruptly inward in front, with a lowering of the superior border, 
to meet the dentary of the opposite side in a ligamentous connexion behind 
the predentary. The mandibular fossa excavates the coronoid process 
behind, and internally is continuous with the Meckelian groove wTich 
lessens in depth in its forward course near the lower border of the bone, 
and disappears in advance of a point in line with the front end of the 
magazine. Behind the magazine the dentary ends in a laterally 
compressed, pointed process, internal to the mandibular fossa. This 
process is covered on its inner face, and embraced above, by the anterior 
end of the splenial. Posteriorly beneath the Meckelian groove, is a 
narrow surface marking the internal application of the angular as far 
forward as a point nearly beneath the midlength of the magazine. Pos- 
teriorly below the dentary is transversely broad, thin, and obtusely pointed 
at its termination, underlapping the surangular so that the floor of the 
mandibular fossa is continuous on the upper front surface of the surangular. 
The narrow symphysial surface is deeply grooved from front to back. 
The dental foramina, corresponding in number to the vertical series of 
teeth, are conspicuous internally following the lower curve of the magazine. 
At the anterior end externally is a rather large foramen behind which are 
six or seven smaller ones at irregular intervals back to the front of the 
magazine. Still farther back are a few other foramina in the outer face 
of the bone. 
In the dentary there are forty-eight or forty-nine vertical series of teeth 
with four or five teeth and sometimes the stump of a sixth in each series. 
The individual teeth are largest at the midlength 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 enam- 
elled 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. There are about 230 teeth in each dentary, this being many less 
than the number (406) ascribed to Diclonius mirahilis by Cope in his 
description of that species in 1883. 
Measurements of Left Deniary of Edmontosaurus, Cat. Xo. 2289. 
Mm. 
Length about 780 
Thickness at midlength and midheight of dental magazine 58 
Distance of inner edge of cutting surface of teeth, at midlength of magazine, above 
lower border 190 
Depth of bone just in advance of first vertical series of teeth 150 
Distance of top of coronoid process above lower border of dentary 297 
Length of dental magazine at its midheight 366 
