242 
PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 
the earlier and more primitive genera, though it may be seen that in 
Thomas hux ley a and Asmodeus the premaxillae are relatively very large ; 
there is a considerable diastema between the canine and external incisors 
and all of the incisors are arranged in nearly the same fore-and-aft line as the 
grinding teeth, making the muzzle long and pointed. In the Santa Cruz 
genera the premaxillae are greatly reduced, the incisors are in a transverse 
row and the muzzle and chin are abruptly rounded. The nasals are much 
shortened and the anterior nares greatly enlarged and are no longer ter- 
minal in position. The zygomatic arch does not rise so high upon the 
side of the cranium and the tympanic bulla is much larger than in the 
Toxodonta. 
Hardly anything is known of the vertebral column, and limb-bones have 
been found in association with only a very few of the genera. There is 
no coossification of the fore-arm or leg bones, nor any loss or fusion 
among the bones of the feet, so far as these elements are known. In 
Asmodeus of the Deseado stage, and in Homalodontotherium the humerus 
is extremely massive and is remarkable for the great development of the 
deltoid crest, the external epicondyle a‘nd the supinator ridge, and in 
Asmodeus and Diorotherium an entepicondylar foramen is present. The 
fore-arm bones are very long and stout, quite as in the Chalicotheres, but 
without any tendency to coossification ; the radius has a relatively small 
head, with more or less power of rotation upon the humerus, and very 
heavy distal end. The ulna is also very stout, especially in Asmodeus , 
in which it does not taper so much distally as it does in the Santa Cruz 
genus. The femur, which is known only in Homalodontotherium , is some- 
what proboscidean in appearance, owing to the antero-posterior com- 
pression and flattering of the shaft, but the third trochanter is large and 
conspicuous, though not very prominent. The leg-bones, likewise known 
only in the same genus, are proportionately short. The tibia is very heavy 
and broadens distally, where it extends over and rests upon the fibula. 
The latter has a stout, subcylindrical shaft and very massive distal end, 
with large, oblique facets for the calcaneum and astragalus. 
Aside from Leontinia , which will be considered below, the very curious 
feet are not at all fully known except in the Santa Cruz genus. The 
manus is pentadactyl, with interlocking carpus and relatively very long 
metacarpals, of which the fifth is considerably the stoutest ; the distal 
trochlea is curiously recessed and thrown back of the axis of the shaft. 
