Blastoids
Blastoids were small, stemmed
echinoderms, abundant and diverse in the Middle and Late Paleozoic. Usually
only the globular theca, covered by regularly arranged plates , is preserved.
5 petal-shaped areas extend from the mouth, at the center of the upper side of
the theca, partway down the sides of the theca. In life, threadlike arms
projecting upward from the sides of the petals were used for feeding. The anus
is located between the petals, near the mouth. Additional, round or slitlike
openings near the mouth were for the discharge of water.
DIRECTORY