Definitions

Chitinous or more or less calcified covering of the head region, formed of fused tergites of cephalic somites, commonly having pleura. [McLaughlin, 1980]
Chitinous, more or less calcified covering structure of head region formed of fused tergites of cephalic somites commonly having pleura. [Moore and McCormick, 1969]
Head shield; the dorsal head tergites fused to form a solid cuticular plate, often with ventrolateral folds ("pleural folds"). [Brusca and Brusca, 2002]
(Taxon-specific: Class Cephalocarida) Broad, semicircular shield covering dorsal surface of head. Formed by fusion of dorsal surfaces (tergites) of first five segments.
(syn. head shield) [Stachowitsch, 1992]
(Taxon-specific: Subclass Copepoda) Dorsal cuticular shield covering head and thoracic somites (thoracomeres) fused to it. May project anteriorly to form rostrum, posteriorly to form pair of alae. (convex, flat, regionated).
(syn. head shield, dorsal shield) [Stachowitsch, 1992]
(Taxon-specific: Class Remipedia) Shield-like cuticular structure dorsally convering and folding over front of head (cephalon) and extending somewhat laterally and posteriorly; tapers anteriorly (in one case with narrowest part in middle) and is marked by one or two transverse grooves. (subquadrangular, subrectangular, subtrapezoidal).
(syn. head shield) [Stachowitsch, 1992]