Cope.] 554 (Jan, 18, 
cess is directly below its anterior border. Thus the tympanic bone is 
directed obliquely downwards and forwards. Posteriorly it is separated 
by a groove from the mastoid process. Anteriorly it is separated by a fossa 
from an osseous mass which occupies the space between it and the post- 
glenoid process. Before the skull was reconstructed from its fragments, this 
mass was observed to be entirely distinct from the postglenoid process, 
which it equals in height. Continuous with it, there descends another 
osseous body to near the line of the extremity of the mastoid process, with 
a truncate inferior edge, which is separated from the otic bulla by an open 
grooye. The stylohyal ligament is probably inserted into a fossa at the 
anterior extremity of this groove. The postglenoid process is low and 
more extended transversely. The anteroposterior diameter is small. The 
glenoid surface is much extended transversely and terminates externally in 
a slight thickening. The zygomatic process of the squamosal bone is at 
first expanded horizontally and has a low convexity of the thin superior 
edge. Its vertically compressed portion is entirely supported by the ma- 
lar, and does not extend so far forwards as the anterior edge of the 
zygomatic foramen. The malar bone is remarkable for the depth of its 
suborbital portion, which fully equals the diameter of the orbit. Its infe- 
rior edge presents a thickened angle downwards below the anterior part of 
the last superior molar. Its superoanterior angle terminates in a promi- 
nent rib of the side of the face, which extends along the inferior edge of 
the facial vacuity, Beneath the anterior part of the latter the face is con- 
cave, Above this concavity the ascending plate of the maxillary is con- 
vex in the vertical section, turning inwards at the apex to unite with 
the lateral part of the extremity of the nasal bone. The preorbital fossa 
is small and looks forwards and upwards. 
The otic bullee are larger than in any other Oreodontid. They are of a 
short oval form, somewhat truncate anteriorly and posteriorly. Thus they 
differ from those of CO. simus, where they are elongate-oval. They only 
reach as far anteriorly as the middle of the internal extremity of the 
glenoid surface ; while in C. simus they reach the line of the posterior 
outline of the zygomatic foramen. They terminate near the inferior inter- 
nal point, in a little acute osseous apex, which is smaller than in (. simus. 
The bull approach so closely together that the bassioccipital is much nar- 
rowed, and the sides of its inferior surface are excavated so as to reduce 
the middle line to a narrow acute keel. The lateral excavations follow the 
posterior internal base of the bulls, leaving a median table, which is itself 
excavated by a shallow fossa, which extends from the median keel to the 
foramen magnum, The median keel disappears anteriorly. The sphenoid 
is protuberant downwards as a narrow convex rib, which rises and disap- 
pears in the presphenoid,. The descending sphenoid ala forms the posterior 
boundary of the posterior nareal trough, and makes a strong angle with 
the pyramidal process of the palatine, which is turned outwards. The 
pterygoid squama terminates in an apex which points downwards and 
posteriorly towards the apex of the otic bulla. The palatonareal border is 
