LIFE IN THE PAST 171 
nal sea which spread over what is now known as the 
Mississippi Valley. Everywhere over this region must 
have grown in the shallow water great numbers of 
creatures called crinoids or stone lilies. They were 
attached to the bottom by slender stems, sometimes 
many feet long. These stems are jointed, and when 
they became fossilized the sections were apt to sepa- 
rate, with the result that over a wide area in the 
Mississippi Valley it is very common to find these 
little segments which look not unlike checkers. At the 
end of the stem was a rounded head, with a mouth 
at the top, and around the mouth were branched, 
feathery arms. The creatures must have been ex- 
quisitely beautiful, but they have completely disap- 
peared from the face of the earth, with the exception 
of a very few, found in the obscurity of the almost 
fathomless depths of the great ocean. Here they 
remain as peculiar relics, only preserved by the un- 
varying conditions in the deep sea from the extinc- 
tion that has met their sisters. 
Those who are familiar with our seacoast will know 
an interesting creature known as the horseshoe crab, 
or king crab, though in reality it is not a crab at all. 
It is rather more nearly related to the spiders than 
the crabs, though no one but a technical zodlogist 
could possibly associate them together. The ancestors 
of these king crabs were the finest and best developed 
