Paleontology. 185 
belonged to a very early mammal, antecedent to the 
elephant series, the horse series, the rhinoceros, the 
hog, and, in short, all the known hoofed mammalia 
(Fig. 80). It was presumably an inhabitant of 
swampy ground, slow in its movements, and low in 
its intelligence. 
But now,as we have seen for more rapid progression 
on hard uneven ground, a stronger and better jointed 
foot would be needed. Therefore we find the bones 
of the wrist and ankle beginning to interlock, both 
among themselves and also with those of the foot and 
hand immediately below them. Such a stage of 
evolution is still apparent in the now existing elephant. 
(See Fig. 81.) 
Next, however, a still stronger foot was made by 
the still further interlocking of the wrist and ankle 
bones, so that both the first and second rows of them 
were thus fitted into each other, as well as into the 
bones of the hand and foot beneath. This further 
modification is clearly traceable in some of the earlier 
perissodactyls, and occurs in the majority at the 
present time. Compare, for example, the greater in- 
terlocking and consolidation of these small bones in the 
Rhinoceros as contrasted with the Elephant (Fig. 81). 
Moreover, simultaneously with these consolidating im- 
provements in the mechanism of the wrist and ankle 
joints, or possibly at a somewhat later period, a reduc- 
tion in the number of digits began to take place. This 
was a continuation of the policy of consolidating the 
foot, analogous to the dropping out of the sixth row 
of small bones in the paddle of Bapfanodon. (Fig. 
78) Inthe pentadactyl plantigrade foot of the early 
mammals, the first digit, being the shortest, was the 
