1879.) Extinct American Rhinoceroses and their Allies. 7714 
the tapiroid feature of the non-closure of the auditory meatus 
below by the posttympanic process; and the postglenoid process 
is generally more like that of the-tapirs than are those of the 
later genera Aphelops and Rhinocerus. The form of the femur is 
also quite characteristic, presenting tapiroid characters again in 
the shape of the great trochanter. This process is not flat and 
obliquely truncated as in the genera above named, but is horizon- 
tal proximally, and with a produced recurved apex and posterior 
crest, which bound a large fossa. The species are the smallest of 
the family, the A. mite having the dimensions of the Malayan 
tapir. 
In the species of Diceratherium (Marsh) the cranium and limb 
bones present the characters above ascribed to the Aceratheria, 
In size they are intermediate between the latter and the Aphe/opes. 
The two American species are known from the beds of the 
Truckee epoch of Oregon; a third species, D. pleurocerus (Duv.) 
has been found in France. 
Aphelops (Cope) occupies a position intermediate between Acera- 
therium Kaup and Rhinocerus Linn. 
agrees with the former in the presence 
of incisor and canine teeth, and in the 
absence of indication of a nasal horn, 
but differs from it in lacking the fifth 
digit of the anterior foot. In the last 
respect it is identical with the genus 
XRhinocerus, differing from it in characters 
already mentioned, in which it agrees 
with Aceratherium. From Atelodus Pom. 
it differs still more widely, as that genus 
wants incisor and canine teeth. 
The evidence on which this genus 
rests is furnished by two species, the 
Aphelops megalodus, and the A. fossiger. f 
In both of these animals, the number of A 
anterior digits is known to be only three ~ 
and in the former the inferior canines 
and alveoli for incisors can be seenin p, iis E aie Gan 
the specimens. In two other species above, posterior view of skull. 
Fic. 6,—A. fossiger, skull fig- 
provisionally referred to the same genus, ured i in Figg one-sixth natural - 
the A. crassus and A. malacorhinus, the siz 
digits and incisor teeth are unknown but ae last named species 
was certainly hornless, and it is supposed that the first named was _ 
