AKTIODACTYLA. 
357 
the species above described, and its reference to this genus is provisional only. 
The horns have a compression in the proximal portion like those of the 
other species, and may very possibly be divided in the same manner at a 
point beyond the portion of the beam exhibited by the specimen. 
The horns stand immediately above the orbits as in the Antilocapra, but 
while they present a face outward, they present a still wdder one backward 
to the zygomatic fossa. This is due to the fact that there is no oblique 
horizontal crest connecting the orbit with the j)arietal region, as in the Deer 
and Sheep, the postorbital process descending directly from the base of the 
horn. The parietal region is rather more* contracted than in either the 
Sheep or Deer, while the frontal region is expanded and slightly concave 
in the transverse direction. There is no free superciliary border at the base 
of the horn, as in B. furcatus and B. necatus. The section of the beam near 
the base is a regular oval, the long axis directed longitudinally and a little 
outward in front. The beam is erect, with a slight curvature outward near 
the base. The tissue is rather more spongy than in the species named; 
The supraorbital foramen is large, and issues near the anterior inner base 
of the horn. The interior face of the parietal bones displays the impression 
of three superior longitudinal convolutions of the cerebral hemispheres. 
Measurements. 
M. 
Outer width between the bases of the horu-cores. 0.112 
Inner width between the bases of the horn-cores. 0. 055 
Width of the temporal fossa behind the horns. 0. 053 
Long diameter of the horn-core.. 0. 028 
Short diameter of the horn-core. 0. 021 
Length of the part preserved... 0. 033 
Dicrocerus trilateralis, Cope. 
Plate Ixxxi, fig. 8; Ixxxii, figs. 7-9. 
This species is the largest of the Deer-antelope here described, portions 
of the jaws and teeth equaling in dimensions corresponding parts of the 
Red Deer {Cervus elapJms). I discovered the bones lying on a gentle slope 
of sandy rock in three little collections, each two feet from the others, and 
in a straight line : in one of these were found portions of the pelvis and ster¬ 
num and a fragment of a horn; in another, portions of the mandible, with 
teeth; in the third, fragments of ribs. They are all in the due proportion 
