98 The Suessonian Fauna of North America. © [February, 
lobes display a great development in comparison with the cere- 
bral hemispheres.” : 
The Wahsatch horizon is lower than the oldest above referred 
to by Professor Lartet, and it is interesting to observe how his 
generalization with reference to the characters of the mammalian 
brain is confirmed. The Ozyena forcipata approaches more 
nearly to the viverrine type than to any other form of the Car- 
nivora, although separated by a wide interval. I have been 
able to obtain a cast of the superior and anterior portions of its 
cranial chamber, from which it appears that the brain possessed 
characters of a much lower type than that observed in the V. an- 
tiqua. The olfactory lobes are enormously developed, rising 
higher than the hemispheres, from which they are not only en- 
tirely free, but are separated by a constriction of their basal por- 
tions. The hemispheres are not wider at the middle than the ol- 
factory lobes, and have therefore elongated proportions. Their 
superior portion is without conyvolutions. Although not a mår- 
supial, the general form in Ozxyena is more like that of the opos- 
sum than that of any other living animal, but is still lower in 
character. Its inferiority is especially seen in its small size. 
The mandibular ramus of the O. forcipata is about the size of 
that of the jaguar, but the brain, even with its large olfactory 
lobes, is only about two thirds as long, and one third as wide. 
The ankle-joint presents a great simplicity of structure in most 
of the Wahsatch mammals, both flesh-eaters and hoofed types. 
The astragalus is nearly flat, and not like a segment of a pulley 
as in most existing Mammalia, and it therefore permitted but 
little flexure of the foot on the leg. The only exception to this 
rule is found in the species of Hyracotherium and allies of the 
order Perissodactyla, which number ten species out of a total of 
fifty-four. 
As regards the elbow-joint a similar peculiarity was discovered 
to exist. In the majority of existing mammals, a ridge or bead 
divides the two facets of the humerus, which receive the ulna 
and radius respectively ; it is called the intertrochlear ridge. In 
the ox and horse this ridge is very near the external border of 
the humerus. In the mammals of the Wahsatch beds this ridge 
was found to be wanting, excepting in the ten species of Peris- 
sodactyla above mentioned. 
In respect to the teeth, no species presenting the selenodont 
or double-crescent bearing type had been found. Of the simpler 
types, where tubercles are united into crests, twelve species out 
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