30 ANIMALS OF THE PAST 
tered through the rocks were arranged. For 
the teeth were not planted in sockets, as they 
are in higher animals, but simply rested on the 
jaws, from which they readily became detached 
when decompositign set in after death. To 
complicate matters, the teeth in different parts 
of the jaws were often so unlike one another 
that when found separately they would hardly 
be suspected of having belonged to the same 
animal. Besides teeth these fishes, for pur- 
poses of offence and defence, were usually armed 
with spines, sometimes of considerable size and 
strength, and often elaborately grooved and 
sculptured. As the soft parts perished the 
teeth and spines were left to be scattered by 
waves and currents, a tooth here, another there, 
and a spine somewhere else; so it has often 
happened that, being found separately, two or 
three quite different names have been given to 
one and the same animal. Now and then some 
specimen comes to light that escaped the 
thousand and one accidents to which such 
things were exposed, and that not only shows 
the teeth and spines but the faint imprint of 
the body and fins as well. And from such rare 
