Acorn barnacle and acorn shell are vernacular names for certain types of stalkless

barnacle A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive ...

s, generally excluding stalked or gooseneck barnacles. As adults they are typically cone-shaped, symmetrical, and attached to rocks or other fixed objects in the ocean. Members of the barnacle

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Balanomorpha The Balanomorpha are an order of barnacles, containing familiar acorn barnacles of the seashore. The order contains these families: * Austrobalanidae Newman & Ross, 1976 * Balanidae Leach, 1817 (acorn barnacles) * Bathylasmatidae Newman & Ross ...

are often called acorn barnacles. Acorn Barnacles - Flickr - brewbooks

In addition, several species of barnacles are specifically called by the common name "acorn barnacle", including: * '' Balanus glandula'', Common Acorn Barnacle * ''

Balanus nubilus ''Balanus nubilus'', commonly called the giant acorn barnacle, is the world's largest barnacle, reaching a diameter of and a height of up to , and containing the largest known muscle fibres. ''Balanus nubilus'' is a northeast Pacific species t ...

'', Giant Acorn Barnacle * ''

Chthamalus antennatus ''Chthamalus antennatus'', the six-plated barnacle is a species of intertidal barnacle found in eastern and southern Australia. Growing from two centimetres wide and one centimetre high. The barnacle is found on the coast, usually on rocks at or ...

'', Acorn Barnacle * ''

Megabalanus coccopoma ''Megabalanus coccopoma'', the titan acorn barnacle, is a tropical species of barnacle first described by Charles Darwin in 1854. Its native range is the Pacific coasts of South and Central America but it is extending its range to other parts of ...

'', Titan Acorn Barnacle * ''

Megabalanus tintinnabulum ''Megabalanus tintinnabulum'' is a species of large barnacle in the family Balanidae. It is the type species of the genus. The specific name comes from the Latin ' meaning a handbell and probably refers to the fact that small groups of barnacles ...

'', Titan Acorn Barnacle * ''

Paraconcavus pacificus ''Paraconcavus pacificus'', the red-striped acorn barnacle, is a species of balanid barnacle known from subtidal sandy habitats of the outer northeastern Pacific coast, from Baja California north to Monterey Bay. It grows to 35 mm in diamet ...

'', Red-striped Acorn Barnacle * ''

Semibalanus balanoides ''Semibalanus balanoides'' (common barnacle, common rock barnacle, northern rock barnacle) is a common and widespread boreo-arctic species of acorn barnacle. It is common on rocks and other substrates in the intertidal zone of north-western Euro ...

'', Northern Acorn Barnacle

References

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