HOLLAND AND PETERSON: OSTEOLOGY OF THE CHALICOTHEROIDEA. 319 
sacral vertebrae, and its anterior margin is not so thoroughly coodssified with the 
spine of the first vertebra as its posterior margin is co6ssified with the anterior 
margin of the third vertebra. Its centrum is smaller than that of the first sacral 
vertebra in all of its dimensions. 
The Third Sacral Vertebra. 
This vertebra is, like its predecessor, only known thus far in the codssified 
state in which it appears in specimens No. 1704 and No. 1706. While its centrum 
in its dimensions is less than those of the two preceding sacral vertebre, the neural 
spine is longer and more massive in all dimensions than is the case in these, and 
marks the climax in development of this portion of the sacrum. It is strongly 
coossified on its anterior and posterior margins with the neural spines of the second 
and fourth sacral vertebre. 
The Fourth Sacral Vertebra. 
The centrum is smaller in all of its dimensions than those of the three pre- 
ceding sacral vertebre. The neural spine is only known from specimen No. 1706. 
It is appressed against and codéssified with the posterior margin of the spine of 
the third sacral vertebra. The antero-posterior diameter of the spine is less than 
that of the third sacral vertebra. 
The Caudal Vertebre. 
Until the present time no caudal vertebrze, which can with positive certainty 
be identified as belonging to the various specimens of Moropus obtained at the 
Agate Spring Quarries, have been found. The ungulate mammals occurring in 
the quarry belonged to the genera Diceratherium, Dinohyus, Stenomylus, and 
Fic. 73. Caudal vertebra of M. elatus (No. 2144). Fie. 74. Caudal vertebra of M. elatus (No. 1823). 
<4. 1, dorsal, 2, ventral, 3, lateral, 4, anterior, 5, <4. 1, posterior, 2, anterior, 3, lateral, 4, superior, 
posterior, views. 5, inferior, views. 
Moropus. Fortunately some specimens belonging to the first-named genus were 
found with their caudal vertebre articulated and in place, so that the identification 
of the caudals of this genus has been removed beyond the sphere of doubt. The 
