|Abstract: ||Abstract: The genus Chthamalus (Cirripedia: Balanomorpha) is distributed in the high intertidal on rocky shores all round the world (Newman & Ross, 1976) of which 15 species are well enough described to assign to one of the four groups including the ‘challengeri’, ‘¢ssus’, ‘stellatus’ and ‘malayensis’ group (Southward et al., 1998). In the west Paci¢c region, ¢ve species have been recorded (see review by Southward & Newman, 2003): (1) Chthamalus antennatus, common in southern Australia (Newman & Ross, 1976); (2) C. challengeri, dominating the Japanese, Korean and Chinese coastlines (Newman & Ross, 1976); (3) C. sinensis in the South China region (Ren, 1984); (4) C. malayensis, covering the Andamans to Taiwan (Pope, 1965); and (5) C. moro, which is regarded as an independent species recorded in the South China Sea and Philippines, contrary to the opinion that it is a synonym of C. malayensis Pilsbry (Ren, 1984; Poltarukha, 2000). In Hong Kong, only C. malayensis has been recorded previously, which occurs high on the shore of oceanic coasts (Foster, 1982; Morton & Morton, 1983; Yan & Chan, 2001). The morphology of the parietes of Chthamalus can be variable and this has caused confusion in di¡erentiating species (Dando & Southward, 1980). Careful examination of the opercular plates, arthropodal and larval morphology, however, has allowed workers in recent years to distinguish closely related species (e.g. C. montagui was separated from C. stellatus, Southward, 1976; Burrows et al., 1999; C. proteus from C. fragilis, Dando & Southward, 1980 and C. southwardi from C. malayensis, Poltarukha, 2000). In the present study, an unidenti¢ed Chthamalus species was found in the mid-intertidal region of exposed
shores in Hong Kong. Adult and larval morphology of this species did not match any descriptions of recorded Chthamalus species. It is, therefore, considered a new species.