Type material of Bangia vieillardii Kütz. from New Caledonia has been studied and determined to belong to the green algal genus Chaetomorpha. The name Chaetomorpha vieillardii (Kütz.), n. comb., is effected, and this binomial is proposed to serve for what has previously been known in tropical seas as C. crassa. Genuine C. crassa (C. Agardh) Kütz., based on European type specimens, has been treated by others to be conspecific with C. linum (O. F. Müll.) Kütz.