P.677 - §8 Toward the close of the final Silurian submergence there is a great increase in the echinoderms--the stone lilies--as is evidenced by the crinoid limestone deposits. The trilobites have nearly disappeared, and the mollusks continue monarchs of the seas; coral-reef formation increases greatly. During this age, P.678 - §0 in the more favorable locations the primitive water scorpions first evolve. Soon thereafter, and suddenly, the true scorpions--actual air breathers--make their appearance.
crinoids are stone lilies or sea lilies that appeared during the Ordovician period..
