Balanomorpha

(invertebrate zoology) The symmetrical barnacles, a suborder of sessile crustaceans in the order Thoracica.

A suborder of the Thoracica. This group includes the common acorn barnacles. The mantle secretes a highly calcified test forming the bilaterally symmetrical conical shell, consisting typically of anterior rostrum, posterior carina, and one to three pairs of lateral plates. The broad basis is membranous or calcified. The shell (mantle) opening is closed by paired valves, each formed of two interlocking plates. These animals are hermaphroditic, and cross-fertilization is normal. Dwarf males have been recorded.

Balanomorph barnacles are found on almost every possible site for attachment, inanimate or living. They are most abundant intertidally and in shallow water. Some species occur at great depths. A few have become an economic problem as fouling organisms on ship hulls and in marine installations. See also Barnacle.