The occurrence near Livorno (Ligurian Sea, Italy) of Caulerpa racemosa
(Forsskal) J. Agardh (Chlorophyceae, Caulerpales) is reported. Up to
now, the southeastern Mediterranean has constituted the northernmost l
imit of distribution of this species, as indicated by previous algolog
ical studies. The hypothesis that the distribution of C. racemosa coul
d spread, is put forward. The characteristics of this alga and its hab
itat are described.