1895.] Geology and Paleontology. 1085 
region of the skull. Anteriorly both the skull and lower jaw are well 
preserved, and supplement admirably Prof. Marsh’s type of this genus 
which consists only of the palate and premolar and molar teeth. 
The present species is at once distinguished from D. elatus by its 
greater size, as is shown by a comparison of the length of the premolar 
and molar series, which is 310 mm. in the former and 242 in the latter. 
The Cranium :—In general appearance the cranium of D. emargi- 
natus is remarkably like some of the smaller forms of Titanotherium. 
The dorsal surface is slightly concave antero-posteriorly? and is 
further characterized by the absence of a sagittal crest. The nasal 
openings are high and deeply incised. The horns are composed of both 
the frontals and nasals; they are placed transversely and directed up- 
ward, outward and forward; they are elliptical in cross-section with 
the antero-posterior diameter the longer. The nasals are broad, strong 
and rather short, they are firmly codssified, concave inferiorly, emargi- 
nate anteriorly and with their external lateral borders considerably 
thickened, they do not extend as far forward as the premaxillaries and 
are slightly constricted just in front of the base of the horns. The pre- 
maxillaries are well-developed, are separated anteriorly by a deep 
median notch back of which they are firmly codssified, they extend 
considerably in front of the maxillaries.. The maxillaries are expanded at 
the base of the canines and decidedly constricted between this tooth and 
pm. 2, back of which they expand rapidly in order to accommodate the 
large posterior premolars and molars. The infraorbital foramen is 
situated just above pm. 4. 
The Lower Jaw:—The rami are closely united at the symphysis 
which is very long and oblique, its posterior border is just below pm. y. 
The anterior mental foramen is situated directly below pm. z, between 
it and the premolars there is a slightly excavated and fluted area. The 
rami gradually deepen from before backwards. 
The Superior Dentition :—The superior incisors are placed consider- 
ably forward of the canines, and are arranged in the are of a circle in- 
stead of in a nearly straight line as in Titanotherium; they show a 
remarkable transition from the Paleosyops to the Titanotherium type 
of incisor. The external, lateral incisors are large, pointed teeth, with 
strong, internal basal cingula and rather sharp external, lateral cutting 
edges. The median incisors are much smaller than those just de- 
scribed, but are larger and better developed teeth than the internal 
lateral incisors which are assuming the rudimentary, spherical form 
seen in Titanotherium. Both the median incisors and the internal 
laterals have posterior, basal cingula and a posterior ridge connecting 
