No. 492] SOME AMERICAN CHALICOTHERES 747 



between the radius and ulna is, however, well indicated on the 

 distal articulation of the bone. 



The Manus. — The manus of Moropus has four digits, three of 

 which are functional and one (the fifth) rudimentary. This 

 rudimentary fifth metacarpal is not supported by the unciform, 

 but articulates with the fourth metacarpal by fairly well formed 

 facets. Mc.V ^ in No. 1700, Car. Mus. Cat. Vert. Foss., is much 

 slenderer and attains only three-fourths the length of mc. IV. The 

 distal trochlea of mc. V., in No. 1700 is quite imperfect and the 

 digit had perhaps only one phalanx. The trapezium is present 

 and articulates with mc. II, the trapezoid, and the scaphoid, but 

 there is no indication of a first digit. The heavy protuberance 

 on the scaphoid of Moropus which reaches over the trapezoid and 

 articulates with the magnum may be represented by the centrale in 

 Meniscotherium.^ The magnum has a heavy protuberance on 

 the anterior face which extends dorsally and forms, on the distal 

 face, a rough articular surface for the proximal end of mc. II; 

 on the palmar face is a short but heavy hook, and the total vertical 

 diameter of the bone is much greater than is apparent on a direct 

 front view of the manus. The second metacarpal, though shorter 

 than the third and fourth, is the heaviest in the series. The third 

 metacarpal is the longest, consequently the second and third digits 

 in the manus of Moropus supported the greatest weight; therefore 

 the manus is more nearly mesaxonic than was anticipated. It is 

 different from the European genus from Sansan in which mc. I\^ 

 is the longest. 



In the manus of Moropus, the first and second phalanges of the 

 second digit are co-ossified, an important character which Professor 

 Marsh luckily discovered in three different individuals. This 

 now proves to be of perhaps a family importance.^ The ungual 



