72 
BUNOTIIEEIA. 
MAMMALIA. 
BUNOTIIEEIA. 
I. 
Animals wliicli fulfilled the functions of the existing Carnivora were 
abundant in North America during the Eocene period. The Wahsatch 
beds of New Mexico have yielded remains of more than a dozen species 
which ranged from the size of a Weasel to that of a Jaguar. Investigation 
into the structure of these shows, that while they differ in minor points 
among themselves, they agree in possessing characters which distinguish 
them from the true Carnivora. I have already pointed out* that, in the 
genera Amhloctonus, Oxycona^ Stypoloplms, and Didymictis, the tibio-tarsal 
articulation differs from that of the existing Carnivora^ and suggested that 
these forms might prove to be gigantic Insectivora. Further investigation 
satisfied inef that they cannot be included in the order Carnivora, and their 
systematic position has proved to be of considerable interest. 
A greater or less part of the cranial chamber is preserved in specimens 
of Oxymna forcipata and Stypoloplius Mans. In these animals, it has a long, 
narrow form like that of the Opossum, and in the first named, where the 
interior form can be seen, it is evident that the cerebral hemispheres were 
small and narrow, and that the olfactory lobes were relatively large, and 
were entirely uncovered, j)rojecting beyond the hemispheres. 
A study of the dentition, which is largely preserved to us in all of the 
genera, has resulted in establishing the following relations with that of the 
Carnivora. 
Professor Harrison Allen has shownj that, in the human superior molar, 
the anterior inner cusp re2:)resents by continuity the inner root, and he 
calls the posterior inner cusp a cingulum. He rightly supposes that it 
consists of a develojoed basal cingidum ; but as all other cnsps beyond the 
primitive cone have originated in the same way, the completeness of its 
development in Homo, as in other genera, entitles it to the appellation of 
* Systematic Catalogue of the Vertebrata of the Eocene of New Mexico, ISTo, p. 7. 
tOn the supposed Carnivora the Eocene of the Kocky Mountains, Proceed. 
Acad. Phila., 1S75; published December 22. 
+ Dental Cosmos, 1874, 017. 
