ABSTRACT
Darwin was intrigued by a small burrowing barnacle which he collected in Chile during the Beagle voyage and later described as Crypiophialus minutus. Since Darwin, the Acrothoracica have been revised several times, but there is no single feature which unambigously sets them apart from the other barnacles. However, there is little ambiguity as to the identification of presently known species as belonging to the order. The characteristics of the Order Acrothoracica, its families and genera are reviewed. Evidence and speculation on the place of the group within the Cirripedia is presented.
