Cope.] 384 (April 15, 
being immediately below them; I cannot discover whether there is a 
posterior one or not owing to injuries to the specimen. There is apparently 
a fissure-like one on the parieto-squamosal suture posteriorly. The mastoid 
is quite large, expanding downwards and outwards ; it is not so large as 
in a tapir, but much exceeds that in Hyrachyus eximius. The meatus au- 
ditorius eaternus is large, and occupies only the posterior part of the space 
between the postglenoid and posttympanic processes. It is enclosed an- 
teriorly and below by the border of a wide element which may be tympanic. 
It encloses the petrous bone below in a bulla; as however the inner por- 
tion of the best preserved one is broken away, I cannot speak of its rela- 
tions to the basioccipital bone. The foramen lacerum postertus is reduced 
to a jugular and perhaps another connected foramen by the close apposition 
of the petrous bone to the basioccipital for a considerable distance. The 
region of the f. J. medius is injured. Posterior to the f. 1. posterius is a 
foramen opposite the base of the paroccipital process, anterior to the usual 
position of the f. condylowdeum. 
Mandible. The angle of the lower jaw is produced posteriorly, as in some 
species of Hyrachyus: cfr. figs. Vol. IV, U. 8. Geol. Surv. Terrs. The coro- 
noid process is long and is curved backwards to above the posterior border of 
the condyle. There is no tuberosity behind the condyle. The symphysis 
is quite contracted and is short. The mental foramen is below the middle 
of the inferior diastema. The ramus is compressed and at the same time 
strong. 
Dentition. As the deciduous third and fourth premolar teeth, in a worn 
condition, remained in the maxillary bone, I removed them from one side, 
thus displaying the crowns of the corresponding permanent teeth. The 
first premolar may belong to the permanent dentition; the second is the 
deciduous. The former has two roots. The crown is cutting for a short 
distance anteriorly, but posteriorly it expands into a heel, much less de- 
veloped than the internal lobe of the succeeding teeth. The crowns of the 
third and fourth premolars differ externally, as well as in their crests, from 
those of the true molars. The median-anterior and cingular vertical ridges 
are not so prominent as in the latter. The external crest is not divided 
into two by the notch in its grinding face. The anterior cross-crest, at its 
inner or distal extremity, is turned shortly backwards and then inwards, 
giving a “‘pot-hook”’ outline to its triturating surface. The fourth de- 
ciduous premolar presents a peculiar character already ascribed to the first 
true molar. This consists of a crest running parallel with the posterior 
transverse crest and close to it, along its posterior side. It forms the 
border of the tooth for a short distance, but as its direction is slightly 
obliquely forwards as well as outwards, the posterior cingulum appears for 
a very short distance. 
The first true molar is subquadrate in outline. The anterior transverse 
crest commences at the middle-anterior ridge, and is first transverse, then 
directed a little obliquely backwards. The second crest commences at the 
apex of the posterior external crescent, leaving a wide posterior marginal 
