These, with Darwin's three families above mentioned, complete the section of genuine cirripedes now existing.
The vernacular name barnacle, traceable to the fable of pedunculate cirripedes hatching out into bernicle geese, has also been transferred to the sessile cirripedes, which are popularly known as acorn barnacles.
It is generally stated that cirripedes are confined to salt water, and, generally speaking, that is true.
Vaughan Thompson, Zoological Researches (Cork, 1830); memoir iv., " On the Cirripedes or Barnacles, demonstrating their deceptive character."
Under the heading Crustacea the Entomostraca have already been distinguished not only from the Thyrostraca or Cirripedes, but also from the Malacostraca, and an intermediate group of which the true position is still disputed.