White barnacle

Balanus subalbidus

Family Balanidae - barnacles (crustacea)

Shell conical to subcylindrical, made of 6 triangular plates (parietes) fused together with walls (radii) between plates; walls (radii) narrow in conic specimens, wide in subcylindrical specimens; plates are whitish, smooth; no horizontal striations, calcareous base plate, usually stays on hard substrate when barnacle is removed; aperture diamond-shaped except flat or rounded at 1 end; internal plate tergum with wide spur (rounded extension), about 1/3 the width of the basal margin, spur set close to the basal angle.
Similar Species
May be confused with the bay barnacle, B. improvisus. The walls (radii) of the white barnacle are usually more narrow, sometimes almost nonexistent, at least in the conical specimens. The bay barnacle has a radially grooved base. The best way to distinguish these two is by looking at the terga. The bay barnacle has a long spur, and the white barnacle has a short, wide spur. Though sometimes found together, the bay barnacle prefers less saline waters than the white barnacle.
Bay, in lower salinities
Maximum Size
1.3 cm (1/2 in)
Other Common Names
Previous Scientific Names