Echinoidea (Sea Urchins · Overview)
Echinoidea—the class of sea urchins, sand dollars and heart urchins—belongs to the phylum Echinodermata.Their test comprises interlocking calcareous plates bearing movable spines and tube feet;the mouth houses the five‑part jaw apparatus known as Aristotle’s lantern. Echinoids are key grazer...
Crinoids (Overview)
Crinoids (class Crinoidea) comprise stalked sea lilies and unstalked feather stars.They are suspension feeders that capture plankton and particulate organic matter with sticky tube feet on pinnules and convey food along ambulacral grooves to the mouth.Ecology & BiologyFeeding: most efficient i...