Size large, capitulum up to 45 mm (1¾ inches) in length, peduncle up to 6 inches in length. Capitulum enclosed by two large plates on each side and one (the carina) on the back edge. Below these are several rows of small plates, numbering up to a hundred or more, depending upon the age of the barnacle. Surface of peduncle with many small calcareous scales.
Creamy white on the plates, dark brown in the inter-spaces and on the peduncle. The cirri are faintly yellow.
World-wide; in the littoral zone below half-tide mark but only where there is strong wave-action. Occasionally specimens have been found growing on the whale barnacle Coronula diadema, and sometimes on ships.
This is the only pedunculate barnacle found on the British Columbia coast above the low-tide level. Specimens vary greatly in length. Those on the edge of a group usually have short peduncles while those at the centre may have stalks 6 inches long. When a sessile barnacle becomes attached to a plate on the capitulum, in time the outer lamina splits off carrying the sessile barnacle with it, possibly as a result of the tensions set up between the two shells. Such an event provides the only known case where any portion of the calcareous covering of a barnacle is detached during the life of the animal. The peduncle can be used as food. When steamed for twenty minutes and skinned, the flesh is red and tastes like lobster.