250 MEMOIRS OF THE CARNEGIE MUSEUM. 
from the ectoloph by a valley, while the one anterior adheres quite closely to the 
internal face of the protocone, thus forming an inwardly slanting cross-crest. 
Posteriorly and internally the tooth is surrounded by a heavy cingulum, while 
externally it is ighter. D* and D‘ increase progressively in size, and are, as stated 
by Peterson (l. ¢., p. 742), more nearly molariform than are the permanent series, 
which may be observed in the illustrations (see Pl. LI, and Fig. 17). In the speci- 
men (No. 1707) the germ of P? is not nearly as far advanced in development as 
those of P® and P*, as has been plainly brought to light by an excavation which 
has been made close to the alveolar border. 
The inferior milk-incisors are not present in the material at hand, but they 
were most likely there on either side. Dy, has a rather long narrow crown, so that 
in an unworn state the tooth presents a somewhat trenchant crown. Ds is twice 
as long as the preceding tooth and is completely molariform in every respect. 
D, is very little longer than the preceding tooth, but has a greater transverse 
diameter; there is otherwise little or no difference between the two teeth. The 
cingulum is only very slightly developed on the antero-external angle of D3; and 
D, and on the posterior face of D,. Internally the teeth are generally quite smooth. 
THe VERTEBRAL CoLUMN OF Moropus. 
There are seven cervicals, fifteen dorsals, six lumbars, and four sacrals in the 
vertebral column of Moropus. The number of caudals is not known. Judging 
from the size and shape of the sacrals and the distance to be covered by the caudal 
series in order to form only a very short tail, there must have been at least twelve 
caudals. Unfortunately no caudals which can be positively referred to the speci- 
mens in our possession have been found. The tail which has been affixed to the 
mounted specimen is a work of fiction, and while quite probably approximating 
the facts of nature, must not be accepted by students as anything more than a 
scientific surmise. 
The cervicals of M. elatus are relatively very massive; those of M. petersona 
much less so. The centra of the axis and the three succeeding vertebre are laterally 
deeply excavated and their support comes from a narrow and vertically deep 
keel-like ridge on the lower side. The sixth is very broad below, with a great 
expansion of the lateral processes. The seventh is relatively short, and reveals an 
abrupt transition from its predecessors in order to accommodate itself to the dorsal 
series immediately following it. One of the most noticeable features of the cervical 
series is the fact that, with the exception of the atlas, they all have the posterior 
articular surface of the centrum produced below so as to form acup-like depression, 
