Professor Marsh’s Monograph of the Dinocerata. 208 
The position of the axis is the distinctive feature between 
these two types of feet, and not the number of toes, as the 
names usually applied to them indicate. In this respect, the 
terms Artiodactyl and Perissodactyl are misleading, and hence 
the names Paraxonia and Mesaxonia were proposed by the 
author, as substitutes, to express the true axial relation. 
_(5.) In the further reduction of the perissodactyl foot, the 
fifth digit, being shorter than the remaining three, next left 
the ground, and gradually disappeared. Of the three remain- 
ing toes, the middle, or axial, one was the longest, and retaining 
its supremacy, as greater strength and speed were required, 
finally assumed the chief support of the foot, and the outer 
digits left the ground, ceased to be of use, and were lost, 
€xcept as splint bones. The foot of the existing horse shows 
the best example of this reduction in the Perissodactyls, as it 
ot most specialized known in the Ungulate 
it size and power. The fifth digit, for the same reasons as in 
the Perissodactyl foot, first left the ground, and became smaller. 
Next, the second soon foilowed, and these two gradually ceased 
to unctional, or were lost entirely, as in some of the Artio- 
“actyls of to-day. The foot of the goat shows this extreme 
reduction. 
* oo * * * * 
Extinction or Larner MamMats. 
“During the Mesozoic period, all the mammals appear to have 
= small, and it is not probable that any of large size existed, 
T Teptilian life then reigned supreme. ith the dawn of the 
the “ne, Were much larger, and were clearly the monarehs of 
mal, }; about the size of the rhinoceros, was the largest mam- 
» DU 
flourish 
x ne net. he Pl = 
© Proboscidians were the giants of the Pliocene, a 
sn the supremacy in size to-day, but are evidently a declining 
