The inner tunic of the sack ( b ), on each side along the upper half of the orifice, is remarkable from having a moderately broad, curved band of short, sharp spines, not quite so thick as those on the external surface, closely adpressed together and pointing upwards, like the javelins of an ancient phalanx, thus probably preventing the ingress of any intruding animal.
— from A Monograph on the Sub-class Cirripedia (Volume 2 of 2) The Balanidæ, (or Sessile Cirripedes); the Verrucidæ, etc., etc. by Charles Darwin