Z12 CORE ON LEE VPOTHERIA CHAP. 
trochanter, and the unguiculate claws have already been referred 
to. As to the latter, which are short, it is not the end phalanx 
but the first which is retracted; thus Chalicotherium differs 
markedly from both Carnivorous and Edentate types; for in the 
former it is the last phalanx which is retracted, while in the 
Edentates the same phalanx is flexed downwards. The limbs of 
Chalicotherium are nearly of the same size, and the animal 
seems to have been stout and quadrupedal.' 
Macrotherium, like the last genus, seems to have been 
common to both New and Old Worlds. It is to be distinguished 
by a number of characters. It is supposed to have been “ sem1i- 
arboreal and fossorial’”; the fore-limbs are much longer than 
the hind, the relative proportions of the radius and tibia being 
70 to 29. The ulna was distinct from the radius, whereas in 
Chalicothervum the two are coalesced, or nearly so. Young 
specimens appear to possess a full set of incisors; whether this 
is the case or not with Chalicotherium is not known.” 
Homalodontotherium is sometimes placed in the group. 
SUB-ORDER 4. TYPOTHERIA. 
It is a little difficult to be confident that the Typotheria are 
rightly referred to the Ungulata, since they contradict two im- 
portant Ungulate rules. They have clavicles, which are elsewhere 
missing, and the thumb looks as if it were opposable.? An 
Ungulate is essentially a running animal, and has no need of a 
grasping finger. Still Typotheria are placed by most within the 
Ungulate series, though their undoubted likenesses to other 
groups, especially to the Rodentia, are admitted, and indeed 
emphasised. Cope places them definitely with the Toxodonts. 
The Typotheria are an extinct group of smallish beasts, 
confined, like the Toxodontia, to South America, a region which 
during the Tertiary period, and into the Pleistocene, abounded 
with strange and varied types of Ungulate animals. 
The earlier forms of Typotheria may be exemplified by some 
1 See Osborn, American Naturalist, February 1893, p. 118. 
2 It is not absolutely clear whether both or only one genus ranged into 
America. Different opinions have been expressed, 
3 It must be remembered, however, that there is a suggestion of a prehensile 
character in the hand of Phenacodus (see p. 203). 
