Noun
A continuous and, usually, structureless layer which covers more or less of the exterior of many corals.
Source: Webster's dictionaryThis is used by each daughter cell as the larger frustule (or epitheca) into which a second, small frustule (or hypotheca) is constructed. Source: Internet
The dinoflagellate is separated into an upper portion called the epitheca (C) where the apical horn resides (E) and a lower portion called the hypotheca (D). Source: Internet