HOLLAND AND PETERSON: OSTEOLOGY OF THE CHALICOTHEROIDEA. 300 
than in Moropus, and the transverse diameter of the trochlea is relatively smaller, 
due to the narrower capitellum for the articulation with the radius. The anconeal 
fossa is similar in every respect in the two genera, which we are comparing; but the 
supratrochlear fossa is apparently less distinct in the animal from Pikermi. The 
humerus as a whole is relatively shorter and heavier in Nestoritherium than in the 
American genus. 
In Macrotherium, as shown by the illustrations given by Blainville, the humerus 
differs from that of Moropus and Nestoritherium by having the deltoid ridge less 
extended downwardly, by the apparently smaller internal condyle, and by the 
greater development of the lower radial portion of the shaft and the region of the 
entepicondyle. 
MEASUREMENTS OF THE HUMERUS. 
No. 1604 No. 1700 
(elatus), (petersoni), 
mm. mm. 
Greatestplenmo thes ya met tag tet anole ee aati bn aden inOs Bi ticd and) pe Pe eh aes lh 635 464 
sbraniswerceaqatarn versa taMeacinsnse ee ni rar wa atees en Uns Ne sant BO RUN ne nosy) fcet OL) eo aucekante feel 200 150 
ANTREAROGVON GO CUAMNKEE AE INCL 5 oo obo abdobeonesugabogodosdoddsabodensaedcance 160 110 
Greatest transverse diameter at distal end................. 00. cce eee e eee ences 210 142 
INNO VES Che Bib ROC As 4s sanmioee & oe wues bos on blu sorTemie ue Useless oe oleae 144 104 
NMTSEODOStetOnscMamMmetereab GIstalmemds yes sl tec)s neil sel -assied sit cis wsnicie cvel-mege oes) 108 85 
Radius and Ulna. 
(Plate LXVIT.) 
There are a number of individuals, possibly eight or ten, represented by the 
radius and ulna in the Carnegie Museum. 
The radius and ulna are long and slender. In fully adult individuals these 
two bones generally coalesce at least proximally and distally. In M. elatus (No. 
1604) the ulna and radius are codssified throughout, except for a large oblong 
opening between the two shafts a short distance below the head of the radius. 
The Radius.—The head of the radius is very broad transversely in order to 
conform to the broad trochlea of the humerus. Proximally there are two large 
facets for the humerus, which are divided by a prominent ridge. The facet on the 
ulnar side of the ridge is the larger of the two, and forms a shallow basin, while the 
facet on the radial side is more nearly plane. Posteriorly there is a broad attach- 
ment for the ulna, while anteriorly and on the sides the head of the radius is rather 
smooth. The shaft is twisted upon its own axis and is not much widened trans- 
versely, as is generally the case in the early ungulates, rather suggesting the primi- 
tive condition found in the Oligocene oreodonts. In No. 1604 there is a prominent 
