Exterior morphology of the burrowing barnacle Trypetesa lampas (Cirripedia, Acrothoracica)

The external morphology of females and a dwarf male of T. lampas were studi ed. The mantle sack exhibits the structures common to all acrothoracicans, such as: single teeth with associated simple setae on the apertural lips; f eeble multifid scales on the apertural lips and ventral part of the opercul ar region; small mantle teeth and minute multifid setae scattered on most p arts of the mantle sac. The variable denticles were found on the internal s ide of the apertural lips. The big saddle-like labrum and the protopodit of the mouth cirri have an armament similar to lithoglyptid acrothoracicans; both rami of the mouth cirri are covered with a dense carpet of villiform d enticles. The thoracic tappets are reduced to separate and short multifid s cales. The body of the dwarf male lacks cuticular ribs and is covered with minute denticles. Trypetesidae exhibit many charactersistic in common with the Lithoglyptidae: similar form of the mantle sac, a big aperture, well-de veloped labrum and mouth cirri, absence of gut teeth or gizzard, presence o f minute denticles on the male cuticle, form and structure of cyprids. In c ontrast, the Cryptophialidae differs strongly from both the Lithoglyptidae and the Trypetesidae in these charactersistic.