Definition: A sheath; a case; as, the theca, or cell, of an anther; the
theca, or spore case, of a fungus; the theca of the spinal cord.
Definition: The chitinous cup which protects the hydranths of certain
hydroids.
Definition: The more or less cuplike calicle of a coral.
Definition: The wall forming a calicle of a coral.
