276 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. 
this manus was digitigrade, with the phalanges of each digit extending 
forward nearly at a right angle with the metacarpal, as shown in Ame- 
ghino’s Fig. 4, A (’94*, 255) and as Peterson (’07, 746, fig. 26) and 
Barbour (’08, PI. X) have figured the fore-foot of Moropus. Yet the 
manus was capable of some rotation upon the arm and the phalanges 
could be strongly flexed, whatever the use that was made of these 
movements. 
Filhol, on the other hand, restores Macrotherium ( Chalicotherium ) as 
strictly plantigrade both before and behind (’91, PI. XLIII) and Ame- 
ghino expresses still another view regarding the gait of Homalodonto- 
therium: “Ces animaux etaient plantigrades parfaits, dans ce sens, que 
le tarse et la carpe reposaient sur le sol, mais le poids du corps etait porte 
par la partie externe des pieds d’une maniere aussi accentuee que chez 
les edentes gravigrades, ou chez les fourmilliers actuels” (’94“, 60). This 
suggestion does not appear to be a very happy one, for its only support 
is the somewhat larger size of the external digit in both manus and pes, 
and all the articulations involved are radically different in the anteaters 
and the Gravigrada from those in Homalodontotherium. So far at least 
as the pes is concerned, the foot could not be brought to rest upon its 
external border without complete dislocation of the ankle. 
The femur preserved in the La Plata Museum (PI. XXX, figs. 3, 3 a) 
is of somewhat uncertain reference, for, though the evidence for the iden- 
tification as presented by Lydekker (’93, 46) seems very convincing, 
some doubt is thrown upon it by Gaudry’s figures of the leg of Astrcipo- 
therium (’06, 19, fig. 29). Yet the La Plata specimen is by no means 
identical with that figured by Gaudry, despite the strong general resem- 
blance, differing in the following particulars. In A strapotherinni (1) the 
head of the femur is on an even shorter neck and is directed more 
internally; (2) the great trochanter is higher and the second trochanter 
is wanting; (3) the shaft, especially the distal half, is much broader and 
more flattened ; (4) the third trochanter has a more elevated position, is 
shorter proximo-distally and decidedly less prominent; (5) the trochlea 
is extended farther up the shaft. Ameghino’s brief description: “Le 
femur est un os, court, tres large, plat et presque rectangulaire, resemblant 
a celui des edentes gravigrades” (’94*, 60) does not seem to fit the La 
Plata specimen at all and yet Dr. Ameghino pronounced the photographs 
of the latter which I showed him as properly referable to the present 
