146 Wis Jake IABIBS 
elements of the brain-case have been more completely identified than 
has been possible previously and their relations more clearly made 
out. The enclosure of the olfactory canal by the alisphenoids, the 
presence and character of the epipterygoid, here so considered, and 
the relations of the roof bones and the cranial elements are points 
which so far as known have not heretusore been noted. It is hoped that 
these determinations have been made with sufficient accuracy to 
serve for purposes of future comparison. 
Another feature distinctive of this genus, although one mentioned 
by Dr. Williston in his paper previously noted, is the anterior position 
of the external nares. The position of the internal nares behind the 
external also seems to be a new character. 
RELATIONSHIPS OF PALEORHINUS 
In comparing the specimen under discussion with the belodonts 
we may adopt here McGregor’s division of the group into Phytosaurus 
and Mystriosuchus. Tf we include under the former genus the Euro- 
pean forms with high rostrum—Ph. kapjfi and plieningeri—and Cope’s 
species, Ph. buceros, these may be dismissed at once, since the differ- 
ences between this group and Paleorhinus are great enough to be 
considered generic. Fraas in 1896 separated Belodon planirostris 
from the genus and founded a new one, Mystriosuchus, for it, because 
of the great differences in the shape of the snout. The skull of Paleo- 
rhinus presents similar differences, hence its distinctiveness may be 
taken for granted. Of Cope’s species, Belodon scolopax, little can be 
said since that was based on the anterior portion of a rostrum which, 
Cope states, is “shorter but much more slender than that in B. 
plieningeri.” This gives but slight basis for comparison. 
Between Mystriosuchus and Paleorhinus, however, there appears 
at first glance to be an intimate relationship. But, upon closer 
examination, certain features are seen to be widely divergent in the 
) 
two specimens. In the first place, that part of the skull of Paleorhinus 
which lies in front of the anterior point of the nares is one inch longer 
than the portion behind this point. In the case of Mystriosuchus, on 
the other hand, the distance from the tip of the snout to the anterior 
point of the nares is five-sevenths of the entire length of the skull. 
