Burrowing mechanisms of the scalpellid barnacle Lithotrya dorsalis collected from Indian Key, Florida, USA and Fort Point, Jamaica, West Indies, in the fall and spring of 1983 and 1984 were investigated. Calcite spicules covering the peduncule of this animal mechanically abrade carbonate substratum and are described by light and scanning electron microscopy. These spicules undergo a morphological transformation during the molt cycle. Initial observations on the burrowing habit of L. dorsalis indicate that it also employs a chemical agent during bioerosion. Characteristic etching patterns on both optically pure calcite (Iceland spar) and shell material lend further support to this contention. Possible sources of this chemical agent are discussed.