Il THE SERVICE OF TAILS 89 
support of this that the tails of the horse, zebra, 
and other equines, and such large horse-like ante- 
lopes as the gnus, had remained long, and often 
really bushy, because these animals were kickers, 
and able to prevent with their heels any attempt to 
bite this long appendage. A natural corollary of 
this would be the fact that the secretive habits of 
the mice, which live in holes, are mainly nocturnal, 
and are attacked by large animals only by being 
pounced upon or dug out, rendered the length of 
their tails neither helpful nor harmful to them so 
far as enemies are concerned; having probably no 
more to do with their means of defence than have 
their large ears — nor so much! 
Let us, after this digression, return to the main 
line of our story, and ascertain further how certain 
of these appendages serve as weapons, and are 
even armed to that end. 
In the geological long-ago there lived flying 
saurians with long tails; and one of these, de- 
scribed by Professor Marsh, had spines two feet 
long on the side of its tail, running outward and 
backward. 
A fish more unpleasant to meet than even this 
long-departed animal is well known along our 
Eastern coast, as well as in many other parts of 
the world, under the name of sting-ray, or stinga- 
ree. The rays (or skates) are flat, triangular-shaped 
brutes, allied to the sharks in structure; and they 
have slender, whiplash-like tails. That of the 
