446 The American Naturalist. 
only four pairs, and the same number is found among ot 
forms allied at once to the Dasyuride and to the Creodo; 
The larger number of the Creodonts have only three pa 
and, in some genera, but two, and even a single pair. Th 
are some specimens in which one can trace the evolution fi 
the primitive formula. Thus, in the genus Amphiproviv 
the internal pair of superior incisors are entirely atrophied 4 
useless, while the other three pairs are well-developed. 
proves that it is the internal pair of upper incisors that is 
in the passage from the Dasyurian form to the creodont 
carnivorous forms. 
Perhaps the most remarkable specimen discovered during 
the last exploration is a skull almost entire of Borhyena tu 
ata, an animal which has hitherto been known only by so 
insignificant fragments. It is certainly one of the most sin 
lar carnivores that is known. It must have been rather le 
since its skull is 205 millimeters long, and nearly 15 cer 
meters in transverse diameter at the level of the zygomé 
arches. The upper arch of the skull is in an almost horizor 
plane with the cerebral cavity excessively reduced, but 
sagittal crest is very long and well-developed; the fron 
have no postorbital apophyses, and the nasals are wide 
behind in an extraordinary manner; the anterior nasal op 
ing has the characteristic form of placental Carnivora. * 
lachrymal canals open entirely inside of the orbits. Them 
bone is prolonged behind to the glenoid cavity, of wh 
border it forms a part of the boundary as in the Marsupials 
The palate has no palatine foramina. The upper incisors | 
reduced to two pairs, of which the internal one is atrophied. 
Between the canine and the external incisor on each side, 1 
large groove intended to accommodate the lower canine; t 
groove replaces the deep fossa which is found in the 
place in Dasyurus and Amphiproviverra. These groove 
the contraction of the anterior part of the intermaxillary 
followed by the reduction in the number of the incisors, 
the anterior part of the skull the appearance of a rodent. 
canines, premolars, and molars, of each side, form a conti 
series. There are seven molars, of which three are pr 
