STARFISH 61 
enemies, leaving bits of themselves behind them. 
This is a curious, but effective, method of escape. 
Fossil remains of both starfish and brittle-stars 
are found in some of the oldest strata. They are 
often in excellent condition, and quite unmistakable. 
Starfish occur in Cambrian rocks, although not so 
Y 
Palechinus sphericus Holoaster subglobosus (Cretaceous). 
(Carboniferous). 
Echinus Woodwardu (Pliocene). 
Fia. 12.—Fossin Sua-URCHINS. 
commonly as in the Silurian strata, in which both 
they and their relatives, the brittle-stars, are found. 
These creatures, too, have a long pedigree; their 
race has existed from Cambrian times until now. 
Being sea-animals, you will, of course, look for their 
