ON SOME NEW AND LITTLE KNOWN CREODONTS. 
179 
La scissure semble plus elargie que d’habitude et les plis ofFrent moins d’ondulations 
que sur les cerveaux de meme taille appartenant aux espjces actuelles; mais le 
caractere fondamental des cerveaux du quatrieme groupe de Leuret subsiste, et c’est 
pres des Fells et des Hyenes que I’on doit placer le genre Hyenodon.” 
Gervais does not state whether this fragmentary cranium was associated with 
teeth, which would render its reference to Hymnodon unquestionable, and its shape 
does not agree very well with that of the crania figured by De Blainville and Filhol. 
At all events this cranial cast is very ditferent from the characters exhibited by the 
American species, of which I have examined two, H. crucians and H. horridus, the 
former in the Academy’s collection and the latter in the Princeton museum. One is 
forced to conclude either that the brain figured by Gervais belongs to some other 
genus or that the American species differ from the European much more widely than 
has been supposed. 
The cranial cast of H. crucians (partially figured by Dr. Leidy in his Ext. Mam. 
Faun, of Dak. and Neb., PI. II, fig. 2) is essentially unlike Gervais’s specimen. The 
hemispheres are long and narrow, with straight and not very strongly marked convolu- 
tions ; no indication of the crucial sulcus is to be seen ; the limits of the frontal lobes 
are not very clear, but they must have been very small; the temporal lobes are large 
and the sylvian fissure widely open; the olfactory lobes are large and completely ex- 
posed. It is rather difficult to make out the exact number of longitudinal convolu- 
tions ; probably, however, there are three : the sylvian gyrus has a broad posterior 
branch, the anterior being absent. The intermediate and internal gyri are straight 
and show no tendency to undulate or divide, nor are connecting gyri to be seen. This 
brain is not in the least like that of the cats and hyenas, but is more like that of 
Stypolophus ( Cynoliymnodon') as figured by M. Filhol. 
The cranial cast of H. Itorridus, compared with that of H. crucians, is an excellent 
example of Gervais’s principle of an increase in cerebral complexity accompanying an 
increase in the stature of the species. This brain is long and narrow, broadest poste- 
riorly and tapering regularly forwards ; the olfactory lobes are very large and not over- 
lapped by the hemispheres, which also leave the cerebellum entirely uncovered ; the 
temporal lobes are very large and the frontal exceedingly small. Four longitudinal 
convolutions seem to be present; the sylvian gyrus has only the hinder branch de- 
veloped, which bends around posteriorly and joins the external median gyrus ; the 
latter is straight, runs obliquely forward and inward, and at its anterior end joins 
the internal gyrus. The internal median gyrus is very short and joins the internal 
both behind and before ; perhaps it would be better to consider this as simply a par- 
tial division of the internal one. In addition to these a small curved gyrus occurs 
on the frontal lobe. The great difference between this brain and that of H. crucians 
consists in the connection between the convolutions. There is no indication of a cru- 
cial sulcus, and no outward curvature of the median gyrus. Indeed, all the convolu- 
26 JOUR. A. X. S. PHILA., VOL. IX. 
