490 
THE STRUCTURE AND RELATIONSHIPS OF ANCODUS. 
and the chin is abruptly rounded and steeply inclined, while in Ancodus, on the 
other hand, the muzzle is greatly elongated and very low, especially toward the 
front; the chin is pointed and very procumbent. Another difference between the 
two genera consists in the fact that in Ancodus the disproportion between the 
length and weight of the fore- and hind-lirnbs is greater. The neck is also some- 
what more elongated in the latter, though not very much so. In nearly all other 
points the resemblance between the skeletons of the two genera is very close even 
in minor details. 
The proportions of A. americanus are quite different from those of A. brachy- 
rhynchus. The neck is shorter and lighter, the trunk of almost the same length, 
while the limbs are longer and lighter in joroportion to their length. 
So far as can be judged from Kowalevsky’s restoration of Anthracotherium 
(No. 4, PI. XV) the skeleton of that genus differs from that of Ancodus princi- 
pally in the much greater elongation of the trunk and the shortness of the limbs. 
VII. THE EELATIONSHIPS OF ANCODUS. 
Ancodus is usually, and no doubt correctly, classed as a member of the An- 
thracotheriidce, but our survey of its osteology has brought out numerous and sug- 
gestive resemblances to the oreodonts. Both groups display many divergent speci- 
alizations, but at the same time there is a fundamental similarity apparent in all 
parts of the structure, which renders the reference of these likenesses to mere 
parallelism an improbable one. The cranium is closely similar in the two groups 
in almost every detail of construction, except the shape of the occiput, which in 
Oreodon is higher and narrower and with the superior wing-like processes of the 
supra-occipital much better developed. Agriocharus agrees more closely with 
Ancodus in the character of the occiput than Oreodon does with either. The orbit, 
which in the latter genus is completely encircled with bone, remains open behind in 
Ancodus, as is also the case in Agriochoertis and Protoreodofi. The three genera 
further agree in the absence of the lachrymal depression in front of the orbit, which 
is so characteristic a feature of Oreodon. In the proportionate development of the 
facial region Oreodon and Ancodus have diverged widely. In the former the face 
uuii 01 rne race, nowever, varies 
maximum in A. leptorhynchus,. 
