Cope.) 6138 {March 16, 
distance about half as great as the length of the hemispheres without change 
of form. The mass then expands laterally and superiorly, rising upwards 
on each side of an osseous septum, which does not divide the olfactory 
lobes to the inferior face. They are thus deeply grooved above, and 
finally become furcate near to the extremity. Posterior to this point the 
inferior face rises, and the apices project laterally and forwards from the 
superior part of the lobe. The olfactory lobes consist, then, of a massive 
peduncle supporting a grooved subconical enlargement, which is bifurcate 
at the apex.* ; 
Since the internal walls of the skull show the foramina for the exits of 
the cranial nerves, we have a sufficient basis for the determination of the 
parts of the brain. In this attempt we are met by the difficulties which 
are inherent in the use of a cast to represent a brain. Although the fora- 
mini sphenoorbitale and rotundum can be readily fixed, their position is 
such as to give the point of exit of the nervus trigeminus an unusually in- 
ferior position. This appears to be the case to a still greater extent in the 
Uintatherium,}+ where the lateral descending masses are at the same time 
not nearly so largely developed as in Coryphodon. The large inferior area 
enclosed between these boundaries is then homologous with the pons varolit 
or that part of the encephalon which is covered by it. Its appearance in 
Uintatherium supports this identification, but its proportions and anterior 
position in Coryphodon depart more widely from the usual form. The 
two anterior submedian ridges of its surface, faintly indicated in Uinta- 
therium, may be the homologues of the pronounced median ribs in 
Coryphodon which resemble a continuation of the anterior pyramids of the 
medulla oblongata. As they are not very distinctly marked in the medulla 
of Coryphodon, their identification may be uncertain, but they look like 
that portion of the anterior pyramids which is continuous with the crura 
cerebri, and which are concealed in Mammalia by the pons varolii. Their 
prominence in Coryphodon indicates that the pons is wanting in this 
genus as in the Repéilia. A shallow concavity of the sphenoid bone be- 
tween the origins of the trigemini indicates the position of a pituitary body 
or hypophysis. 
* In profile the brain closely resembles in form that of a lizard, ¢.g., an 
‘Amiva, excepting that in the latter the cerebellum is more elevated. 
{he extension downwards and forwards of the middle brain with its pro- 
jection below the hemispheres is common to both, but the inferior portions 
at least, do not appear to be homologous in the two. In the Coryphodon, 
the lateral projections correspond with the exits of the trigeminus from the 
skull; in the Amiva this part terminates in the optic tracts. The superior 
portions of the middle brain correspond in appearance and relative size 
with that of the Amiva, but a clear difficulty in identifying them in the 
* Measurements of this brain are given in the article on Coryphodon elephan- 
topus, in my forthcoming report on the vertebrate Paleontology of New Mexico, 
Vol. IV, of the report of Lieut. G. M. Wheeler. 
+see Amer. Journ. Sci. Arts, 1876, pl. iv, p._165. 
