Beiträge zur Kenntnis der Oreodontidae. 349 
Das Gebiss unterscheidet sich nicht sehr wesentlich von dem 
des Oreodon. Die Schneidezähne sind bedeutend kleiner gewor- 
den; die unteren Caninen sind aber nicht von dieser Reduktion be- 
troffen und in Folge dessen erscheinen sie verhältnismäßig größer, 
Die Backzähne sind schon von Leıpy (Nr. 10, pag. 116) beschrieben 
worden: »In comparison with the true molars of Oreodon the 
erowns are considerably longer in proportion to their breadth and 
are also rather narrower in proportion to their diameter antero-po- 
steriorly, especially in the case of the last of the series. In Oreo- 
don the erowns of the true molars protruded so as to be inserted 
by the fangs alone at a comparatively early period, as in the Deer. 
In Merychyus they successively protruded to the same extent at 
a much later period, as in the Camel. When the crown of the last 
upper molar was yet involved one-third in the jaw, in Merychyus, 
the usual interspaces separating the inner and outer lobes of the 
1° molar and the anterior interspace of the 2" molar had become 
obliterated. In Oreodon the corresponding interspaces were retai- 
ned long after the eomplete protrusion of all the molars. In Mery- 
chyus the outer and inner constituent lobes of the upper true mo- 
lars are closer and the crescentic interspaces more contracted than 
in Oreodon. The external faces of the outer lobes are larger, less 
sloping and more uniformly concave in the transverse direction. 
They are slightly convex longitudinally and generally undivided by 
a median ridge. The internal surfaces of the inner lobes are more 
coneaye vertically. In the unworn upper true molars of Mery- 
chyus the crescentic interspaces or pits are widely gaping, but ra- 
pidly narrow to a vertical fissure. The external face of the inner 
lobes bounding the pits internally, is convex downwards and con- 
cave transversely. The internal face of the outer lobes, bounding 
the pits externally, is nearly vertical. In Oreodon the correspond- 
ing interspaces are more expanded, less deep and gradually slope 
to the bottom. The external face of the inner lobes, bounding the 
pits internally is concave longitudinally and transversely, and the 
internal face of the outer lobes, bounding the pits externally, is 
some what sloping. The buttresses bounding the outer lobes exter- 
nally of the upper true molars of Merychyus are much longer than, 
but do not expand in the same robust manner at bottom as in 
Oreodon. The posterior horn of the antero-internal lobe enters 
the angular internal of the outer lobes, and is joined just before its 
termination by the contiguous horn of the postero-internal lobe. 
