Acorn Barnacle

Acorn barnacle and acorn shell are common names for stalkless barnacles, generally distinguished from the stalked or gooseneck barnacles, and members of the barnacle order Balanomorpha are often called acorn barnacles collectively. As adults they are typically cone-shaped and symmetrical, cementing themselves permanently to rocks or other fixed surfaces in the ocean. Several distinct species carry the specific common name acorn barnacle, including the common acorn barnacle Balanus glandula, the giant acorn barnacle Balanus nubilus and the northern acorn barnacle Semibalanus balanoides.