ON so:me new and little known creodonts. 
157 
tlie unusually long- and deep posterior nares. The limits of the pterjmoidfi are not 
very clear. These bones are long and high, hut as their margms are somewhat broken 
the presence or absence of hamular processes cannot be stated. 
Tlie mandible is very long and rather shallow ; both the alveolar and lower bor- 
ders are strongly curved antero-posteriorly ; the condyle is transverse, strongly convex 
and placed very low, considerably below the level of the teeth. The angle is pro- 
longed into a stout hook, much like that of Stypolophns ; the coronoid process is very 
broad but not high, and rises obliquely from the horizontal ramus. The masseteric 
fossa is large but not deep ; not nearly so marked as in Hyamodon. The symphysis 
is much shorter and broader than in M. lanius. The mandible of Pachycena ossi- 
fraga is very different, aside from its greater size. The angle is not prolonged into a 
hook, the condyle is placed higher, the coronoid notch is wider, and the symphysis is 
much longer. 
The Brain. Owing to the thinness and fragility of the bones, a cranial cast 
could not be attempted, but the partial exposure of the natural cast allows some facts 
to be made out. The cerebral hemispheres are very small, but show some convolu- 
tions ; the cerebellum is relatively large, is lodged in a distinct fossa, separated from 
the cerebrum by a tentorium. 
Dentition. Professor Cope has described the dentition in part, but as this is the 
first specimen in which nearly all the teeth have been found in place it will be neces- 
sary to give some account of them. 
(1) Upper Jaw. The median incisor is small, has a very compressed fang and a 
simple crown ; the second is somewhat larger and the outer very much larger, with a 
long pointed crown, worn on its external side by the lower canine. A considerable 
diastema exists between the outer incisor and the canine. The latter is a powerful 
tooth, in size and proportions much like that of the black bear, though somewliat 
more compressed ; it is very different in appearance from that of M. lanius. The 1st 
premolar follows immediately after the canine without diastema, and in this differs 
from Pachywna which shows diastemata both before and behind the 1st premolar ; it 
has two fangs and its crowm is small and compressed, with the merest rudiment of 
a posterior tubercle. After a small interval, Avhich does not deserve the name of a di- 
astema, comes the 2nd premolar, which is much larger than the finst; it is conical also, 
but has a more developed heel and a distinct cingulum. An interval occurs between 
the 2nd and 3rd premolars, about equal to that between the 1st and 2iid. The 3rd 
premolar is larger than the 2nd and the heel is now almost as. high as the main cusp ; 
there is also a marked increase in thickness ; a small internal tubercle appears opposite 
the heel and a very small anterior basal cusp is present. The homologies of the suc- 
ceeding tooth are somewhat doubtfrd ; I am inclined however, to consider it as the 
4th premolar for the following reasons : (1) In the flesh-eaters, both creodonts and car- 
nivores, the 3rd molar is usually the first tooth to disappear ; (2) the tooth in ques- 
