The Collaborative International Dictionary of English v.0.48:

Endotheca \En`do*the"ca\, n. [NL., from Gr. 'e`ndon within +
   qh`kh a case, box, fr. ? to place.] (Zo["o]l.)
   The tissue which partially fills the interior of the
   interseptal chambers of most madreporarian corals. It usually
   consists of a series of oblique tranverse septa, one above
   another. -- En`do*the"cal, a.
   [1913 Webster]