epithecal

adjective

Of or pertaining to the epitheca, the upper half of the shell of certain types of plankton.

The epithecal covering of the outer is annulated by low ridges and shallow grooves...Fine, close-set, concentric lines, probably representing lines of growth, are obscurely shown on a few of the better preserved portions of the epithecal surface.

See Also: epitheca, hypotheca, hypothecal