The Collaborative International Dictionary of English v.0.48:

Epitheca \Ep`i*the"ca\, n. [NL., fr. Gr. 'epi` upon + ? a case,
   box, fr. ? to place.] (Zo["o]l.)
   A continuous and, usually, structureless layer which covers
   more or less of the exterior of many corals.
   [1913 Webster]