1. Hawksworth, D.L. Nature 334, 301 (1988).
2. Darwin, C. A monograph on the Cirripedia: The Balanidae, Verrucidae etc. (R.Soc., London, 1854).
3. Pilsbury, H.A. Bull. 93 (Smithsonian, Washington, DC, 1916).
4. Newman, W.A. & Ross, A. Revision of the Balanomorph Barnacles (San Diego Soc. Nat. Hist., 1976).
5. Burkhardt, F. & Smith, S. (eds) The Correspondence of Charles Darwin, Vol. 4. (Cambridge University Press, 1988).