capitulum

noun

(L. capitulum: (small) head) (pl. capitula) A type of flowering shoot (see racemose inflorescence) characteristic of plants of the family Compositae (Asteraceae), e.g. daisy and dandelion; the tip of the shoot is flattened and bears many small stalkless flowers (florets) surrounded by an involucre (ring) of bracts; this arrangement gives the appearance of a single flower.
In stalked barnacles, the armored portion within which the appendages and most of the viscera are located.