An intertidal barnacle with six solid wall plates, an oval-
shaped operculum opening, and a membranous base. Juveniles have
a kite-shaped opercular opening. The rostral plate is relatively
narrow, plates are of roughly equal size, and its rostral plate
is not fused with the rostrolateral plates. Usually conical in
shape, however when crowded may become tubular. It may reach a
diameter of approximately 14 mm, depending on habitat, food
availability and level on the shore. The tissue inside the
opercular aperture is bright blue with black and orange
markings.Before 1976 Chthamalus montagui was considered a
variety of Chthamalus stellatus, but in 1976 was identified as a
distinct species, due to differences in its vertical zonation on
the shore and morphology, particularly in the shape of the
opercular plates, setation of the smaller cirri. (Southward,
1976). No one has provided updates yet.