Description
Size small, about one-half inch (10 to 18 mm) in diameter in uncrowded specimens; height, a little more than half the diameter. Shell cone-shaped, cylindrical or club-shaped when crowded. The variation in the structure of the wall-plates is very marked as some have small regular pores with cross-septa, while others have no pores whatever. When the pores are present, they are filled with white powder, which may obscure the cross-septa. About the best distinguishing character of this species is the jet-black lining of the cover-plates. In young specimens there is a translucent triangular area in each scuta through which this can be seen, but in older specimens the plates are too thick for the black lining to show through.
Colour
Usually dirty white or grey.
Distribution
Aleutian Islands to Lower California, chiefly in the intertidal zone. Abundant on rocks; occasionally in brackish water and on ships' bottoms.
Notes
Balanus glandulus is extremely variable in its appearance possibly because of its wide range in habitat.
