532 CHORDATA. 
CURSORIAL ADAPTATION. 
This is not so strongly marked as some of the-others, as it mer 
into the primitive terrestrial. As examples, we may take marsuy 
dog, dog, pig, ox, sheep, rhinoceros, horse, and other Ungulata. 
1. Incidental group: wrséde or bears, mustelide or weasel fam: 
viverride ox civets. They are not well marked off from the primit 
terrestrial, but can on 
occasion move rapidly 
on hard ground. They 
show an incipient raising 
of the body upon the 
toes, a leading feature of 
the cursorial type. 
z. Transition group: 
dog, feide(or cat family), eg 
pig, rhinoceros, tapir, € 
kangaroo. This shows ¢ 
an increasingacquirement 
of the ability to move fast 
over hard ground either 
to catch or to escape. 
The digitigrade mode of 
locomotion is acquired 
and the claws in many 
cases commence to form 
hoofs. Here also com- 
mences a reduction in 
the number of the toes 
to four or three. 
3. True cursorial : 
horse, sheep, ox, deer, 
&c. These types show 
the ultimate cursorial 
modification. The toes 
_are reduced to two, pair- 
ed, or one unpaired, and 
bear hoofs. The clavicles 
tend to disappear. The 
carpus and tarsus are 
reduced and many of 
the elements fuse. The 
proximal elements be- 
come dovetailed into the 
distal (diplarthrous) as a 
palliative against the tor- 
sion due to rapid loco- 
motion on hard ground. 
All these three cursoria 
types are herbivorous. 
