XI CARPUSTAND? DARSUS OF ARDTIODAGD VEES 27) Mt 
the facts of Ungulate descent are absolutely destructive of any 
such comparisons. 
As is the case with the Perissodactyles, the Artiodactyles 
show a historical series, the primitive five-toed condition being 
almost preserved in Oreodon, up to the most modern modification 
exemplified by the Ox, Sheep, etc., in which animals there are not 
even vestiges of the fourth and fifth toes. It has been stated, 
however, that the foetal Sheep has traces of 
those rudiments. The so-called cannon bone 
(the fused third and fourth metapodia) is 
accompanied in its fusion by an increase in 
length. At the same time the functional 
middle metacarpals push aside the rudiments 
and, forming a broad surface for that purpose, 
articulate with the magnum and unciform 
bones to the exclusion of the rudiments. 
This has been termed an “adaptive reduc- 
tion.” In the “ inadaptive reduction ” there 
is the same reduction of the metacarpals, 
but the rudiments still articulate as in the 
primitive Artiodactyle foot, ze. Me IT with 
trapezium, trapezoid, and magnum; Me III 
with magnum and unciform; Me IV and V 
wath unciform. This would appear to give 5, 139.— Dorsal surface of 
greater solidity and consequently greater right tarsus of Red Deer 
strength to the foot. Peale ede 
a, Astragalus; c, cal- 
The carpal bones of the Artiodactyla caneum ; ¢’, cuneiform ; 
: : ; ‘ A te cb, cuboid 5; mIIT, m1V, 
alternate in their articulation; the primi- TWIN 2) Gin HEN 
tive state of affairs’ is not retained even ar. | (From Flower’s 
: : Osteology.) 
in the earliest types. The femur has no 
third trochanter, so prevalent in the Perissodactyles. In the 
hind-foot the caleaneum has an articular facet for the fibula, 
which is not characteristic of the. Perissodactyla. In the more 
modern forms, e.g. the Cervidae, the navicular and cuboid become 
fused into one bone; and there are even further fusions which 
will be referred to later as characteristic features of different 
groups. It is interesting to notice that the reduction begins 
earlier and is clearer in the hind-foot than in the fore. One 
* See, however, p. 196, for a discussion as to which is the more primitive 
arrangement. 
