321 
PAL^OSYOPS LEIDY, AND ITS ALLIES. 
shallow external V’s which are totally without an external cingulum. The median 
buttress of this molar was probably well constricted off. The intermediate conules 
of the last superior molar are small and reduced. The measurements of the 
dental series agree with those of P. IcBvidens, although in the latter species a small 
diastema is present, which is totally wanting in the dentition of P. megarhinus, 
this being a unique character of this species. 
The Skidl (PI. X, fig. 2). — I have referred two skulls in the collection of Prince- 
ton College to this species. The first. No. 10,008, is almost perfectly preserved as far 
back as the glenoid region. The other is an occipital portion. No. 10,041, with the 
auditory processes and basal region finely preserved. The proportions of the facial 
and cranial regions of the skull of this species and their general contour, are 
very different from those oi P. pahidosus. The dorsal contour is without any jjromi- 
nent frontal depression, this part of the skull forming a gradually rising surface as 
far as the middle temporal region, the latter portion being slightly higher than the 
occiifftal. The facial region is very short and strongly compressed at the middle 
portion, with heavy and overhanging nasals. The cranial and facial axes 
form a slight angle with one another. The zygomatic fossa is extremely elongated, 
and the anterior boundary of the orbit is more widely prolonged forward than in 
P. pahidosus. The orbit is extremely small and Bear-like in this species ; it is 
nearly shut off from the temporal fossa by a strongly developed post-orbital process. 
The occipital region is proportionately higher and narrower than in the larger 
forms of the' genus. The occipital crests are strongly compressed, thin and high. 
The sagittal crest is much more strongly developed than in P. pahidosus. It is 
very thin, high and extends farther forward before diverging into the temporal 
ridges than in the latter species. The anterior temporal ridges are weakly devel- 
oped, and the interorbital region narrower and more compressed than in P. pahidosus. 
The narrow and nearly straight zygomatic arch is very different in form from 
that of the allied species of this genus. The shape of the auditory jmocesses is 
another character Avhich distinguishes this species from all others of the genus, with 
the possible exception of P. lavidens. The basal region of the skull is narrower 
than in the larger species. The posterior narial opening is narrow and has its Avails 
strongly compressed. The palate is rather long and narroAv, Avith the roof arched ; 
its posterior margin is rounded AAnth a median prolongation. The posterior limit of 
the palate is at the second molar. 
Nasals and Prcma.villaries (PI. XI, fig. 4.)— The premaxillaries differ in form 
from those of P. pahidosus, they are short Avith a small linear-shaped median sym- 
physis. The anterior aspect of the symphysis presents a prominent median keel. 
Upon each side of the latter the surface of the bone is concave, and is bounded pos- 
teriorly by the prominent canine alveolus. ^TeAved from beloAv the premaxil- 
laries have a decided triangular outline, Avith a short and oblique contour for the 
incisors. The palatal extension of the premaxillaries is more limited in this species 
than in P. pahidosus-, and the large and apparently single incisiA^e foramen is 
