HOLLAND AND PETERSON: OSTEOLOGY OF THE CHALICOTHEROIDEA. 309 
terminates rather abruptly proximally and fits perfectly into a corresponding 
shoulder of the duplex bone already described. The dorsal face is provided with a 
heavy protuberance, but there is no evidence of a hood such as is found on the 
retractile unguals of the carnivores or such as is observed in the edentates. On 
the proximal portion of the plantar face is a heavy subungual process, which takes 
up the entire face of this region and extends well below the articulation for the 
duplex bone. This subungual process of the proximal portion causes a fore-and-aft 
concavity further forward on the plantar face which is well shown in the illustration 
(see Fig. 92,1). On the outer side near the inferior angle of the articulating sur- 
face a large nutrient foramen is invariably shown. 
MEASUREMENTS OF DupPLEX AND TERMINAL PHALANGES OF SECOND Dict. 
Duplex Bone. 
No. 1557. No. 2194 No. 2193 
Y.M. Y.M. Y.M. 
(M. distans), (M. senex), (M. elatus), No. 1604 No. 1700 No. 1424 
type, type, type, (M. elatus), (M. petersoni), (M. hollandi), 
mm mm mm mm mm mm 
Greatestilengthecees isc assests sot se 60 77 100 129 95 86 
Transverse diameter of proximal end... 28 37 sete 60 40 35 
Vertical diameter of distal end........ .. 27 50 66 46 44 
Transverse diameter of distal end...... .. 22 35 43 31 25 
Terminal Phalanx. 
No. 9076 
No. 1604 No. 1700 Y.M. 
(M. elatus), (M. petersoni), (M. Matthewi), 
mm mm. mm 
Greatestilengther a. sas wee. 2 stare ae a eee eam nan. 142 95 148 
Greatestinel abt ers cr eee el taeeie concn ot eee Mone ee 92 62 83 
Greatest transverse diameter of plantar face........... 52 35 35 
The phalanges of the third and fourth digits in Moropus are abruptly reduced 
in size. The proximal articulations for the metacarpals are circular in general 
outline and cup-shaped as in the duplex bone. ‘The proximal ends are extremely 
heavy in comparison with the distal ends. The bones are rather asymmetrical 
in order to conform to the obliquely placed articular facets on the distal end of 
the metacarpals. As is well shown in the illustrations, the distal trochlea is con- 
fined almost entirely to the palmar face and is grooved in order to receive the 
phalanges of the median row. ‘The latter are short and heavy, with a prominent 
median keel separating the articular facets for the proximal phalanges, while 
distally the grooves are more perfectly pulley-like than in the duplex bone of the 
second digit. 
6 [talicized numbers indicate estimated measurements. 
