On the supposed Carnivora of the Eocene of the Rocky Moun- 
tains.—Animals which fulfilled the functions of the existing Car- 
nivora 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 
Ambloctonus, Oxyzna, Stypolophus, and Didymictis, the tibio- 
tarsal articulation differs from that of the existing Carnivora, and 
suggested that these forms might prove to be gigantic Insec- 
tivora. Further investigation has satisfied me that they cannot 
be included in the order Carnivora, and their systematic position 
proves to be of considerable interest. 
A greater or less part of the cranial chamber is preserved in 
specimens of Oxyxna forcipata and Stypolophus hians. 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 evi- 
dent that the cerebral hemispheres were small and narrow, and that 
the olfactory lobes were relatively large, and were entirely un- 
covered, projecting beyond the hemispheres. 
In Ambloctonus, Didymictis, and three undetermined forms, the 
femur supports a third trochanter. In all the genera the ilium 
has a well-marked external anterior ridge, which continues from 
the acetabulum to the crest, distinct from the internal anterior 
ridge. The ilium has, therefore, an angulate or convex external 
face, as in Insectivora and Marsupialia, and does not display the 
usual expansion in a single plane of most of the placentals. In 
all the genera there is a strong tuberosity in the position of the 
anterior inferior spine, which is wanting in the Mammalia, except- 
ing certain Insectivora and Prosimiz,’ although it marks the posi- 
tion of the origin of the rectus femoris muscle in all types. 
The glenoid cavity of the squamosal bone is transverse, and 
well defined anteriorly and posteriorly, as in the Carnivora. Of 
the first series of carpal bones of the four genera named, I have 
been able to learn nothing, but in the genus Synoplotherium from 
the Bridger Eocene of Wyoming, which probably belongs to this 
group, the scaphoid and lunar bones are separate and not united 
as in the Carnivora. 
The above characters point to the Marsupialia or the Insec- 
tivora as the proper location for the flesh-eaters under considera- 
tion ; and the evidence is much more weighty in favor of the lat- 
ter order as their true position. For in the genera Oxyexna and 
Didymictis the posterior part of the inferior border of the mandi- 
bular ramus is not inflected as in Marsupialia, nor are the ante- 
rior inferior iliac tuberosity and third trochanter seen in that or- 
der, while both exist in the Insectivora. 
Cuvier describes* the tibia of Carnivora as follows: “ Quant 4 
' Systematic Catalogue of the Vertebrata of the Eocene of New Mexico, 
1875, p. 7. re 
2 See the figure of Solenodon by Peters, and Chiromys by Owen. 
r 8 Ossemens Fossiles, vii. p. 112. 
