THECA

noun the wall forming a calicle of a coral.

2. theca ·noun the more or less cuplike calicle of a coral.

3. theca ·noun the chitinous cup which protects the hydranths of certain hydroids.

4. theca ·noun 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.