HOLLAND AND PETERSON: OSTEOLOGY OF THE CHALICOTHEROIDEA. 305 
1714, 1714A, and 1714B are small and very immature specimens in a more or 
less damaged condition. 
The spine of the first lumbar is broad, flattened, and projects forward on its 
upper anterior margin. Its extremity is thickened transversely and is rugose. 
The metapophyses in Moropus elatus diminish in the antero-posterior diameter 
of their extremities and are subtriangular in outline, while in Moropus petersoni 
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7 a 
Fig. 64. First lumbar of M. elatus (No. Fig. 65. First lumbar of M. petersont (No. 1708C). X#. 1, 
1604). x4. lateral view; 2, posterior view. 
they do not thus rapidly diminish but are almost as wide at their ends as at their 
origins. ‘The prezygapophysial surfaces occupy the lower anterior half of the inner 
face of the metapophyses in adult specimens of Moropus elatus, and in immature 
specimens a relatively larger proportion of the surface, the metapophysis in imma- 
ture specimens being shorter, while the articulating surface is relatively large. 
In Moropus petersoni the prezygapophysial surface is principally supported on 
the radix and does not impinge greatly upon the inner surface of the metapophysis: 
The first lumbar in M. petersoni has, in fact, a prezygapophysis which in its form 
and arrangement is much like that of the dorsals (see Fig. 65). The postzyga- 
pophyses greatly overhang the posterior face of the centrum. The centrum is 
subtriangular in vertical section at the middle and at both ends. The transverse 
processes are wide, flattened, horizontal spines, which in M. elatus rake slightly 
backward, but in M. petersoni are directed outward at right angles to the axis of 
the vertebra. 
