144 EXTINCT VERTEBRATA FROM THE JUDITH RIVER 
With the remains of Z’rachodon, Dr. Hayden likewise discovered those of a representa. 
tive of the Megalosaurus, to which the name of Deinodon has been applied. 
The specimens upon which the latter genus is based, consist of fragments of about a 
dozen teeth, of which three-fourths are nearly identical in form with those of Megalosaurus, 
while the others are more or less peculiar. The uniformity in shape of the teeth of Me- 
galosaurus would appear to indicate that the three-fourths of the specimens alluded to, be- 
longed to, at most, another species of the same genus, while the remaining specimens 
would typify a distinct genus. However, from the varicty in form of the latter specimens, 
together with the fact that all the specimens present the same general appearance, as re- 
gards colour, texture, and constitution, I have been induced to regard them as belonging to a 
single animal, and feel that it must be left for further discovery to ascertain whether such 
a view is correct. 
The teeth of Deinodon, resembling in form those of Megalosaurus, (figs. 21—34,) are 
laterally compressed conical, with a curvature backward, and with the anterior and pos- 
terior borders trenchant and crenated. In transverse section they are quadrately ellip- 
tical, with acute poles corresponding with the trenchant edges of the teeth. These spe 
cimens, as indicated in figures 25, 29, are generally worn off at the summits, the borders 
extending therefrom, and in several instances at the sides. The attrition of the teeth in- 
dicates those of the upper and lower jaws to have closed upon one another like the blades 
of scissors, so that they were well adapted for penetrating, tearing and cutting their animal 
food. 
Of the remaining specimens of teeth, whose form is peculiar in comparison with that of 
the others, one is the crown of a conical tooth, with feeble lateral compression, and is re- 
presented in figures 46,47. Its transverse section, (figure 48,) is quadrately rotund, with 
two acute angles, corresponding with crenated ridges, one of which occupies the inner side 
of the tooth, while the other is situated postero-externally. The summit of the specimen 
is worn off in a sloping manner anteriorly. ‘The tooth probably occupied a position in 
the back of the jaw. 
A second specimen, represented in figures 37—40, consists of the greater portion of the | 
crown of a tooth whose transverse section forms the half of an ellipse. The anterior bor- 
der is obtusely rounded; the sides are compressed, and the posterior border forms a 
plane, elevated at the middle and bounded by acute crenated margins. The apex of the 
tooth is worn off in a sloping manner posteriorly. 
A third specimen, represented in figures 35, 36, consists of a small fragment of a large 
tooth, like that just described. The latter two specimens perhaps represent canine teeth. 
The last of the aberrantly formed specimens, represented in figures 41—45, consists of 
the crown of a comparatively small tooth, possessing nearly the shape of the two teeth 
