Description
Size small, rarely more than one-half inch in diameter even when uncrowded. Shell conical with rhomboidal orifice. When crowded the shell may be cylindrical and rugged or occasionally club-shaped with the upper part wider than the lower.
The carinal margin of each compartment, from the sheath to the base, projects inward slightly beyond the internal surface of the shell. The basal edge of this projecting margin rests on the calcareous base and is crenated like the basal edge of the remainder of the plate.
Colour
White but with a yellowish "epidermis" covering the shell.
Distribution
North Atlantic and Pacific from the Bering Sea south to Southern California (Santa Barbara). Found mainly below low tide and occasionally in the intertidal zone, often on worm tubes and shells of molluscs and crabs.
Notes
Balanus crenatus has been found as fossils in Pliocene formation in Britain and in Pleistocene deposits of Norway, Maine, Canada, and Alaska, indicating that this species has had a wide distribution in the past. Specimens are also present in the Maywood clay (Interglacial) which is exposed on the beach a mile east of Jordan River, Vancouver Island. On the British Columbia coast B. crenatus is often found associated with B. glandulaand, B. cariosus, and when the shells are crowded it is difficult to distinguish between them. B. crenatus is also commonly found growing on the bottoms of ships; Henry also records this species from brackish water at Port San Juan, B.C. A closely related species, Balanus improvisus , has not yet been definitely recorded for British Columbia. It resembles B. crenatus in all details, except that there is an aductor ridge on the scutum.
