Hardly anything is known about the occurrence of sea-grasses along the Atlantic coast of the South American continent. There are a few records from the coasts of Venezuela and Colombia and only two certain records outside the Caribbean area. The Hydrocharitacean Halophila baillonis Aschers. ex Dickie in Hook. f. (sub nomine H. aschersonii Ostenf.) has been collected once, in 1888, near Pernambuco, Brazil (Setchell, 1934). The other record concerns the leaf-blade of a still unidentified Zostera species, washed ashore near Montevideo, Uruguay, in 1934 (Setchell, 1935; den Hartog, 1970, p. 96). Through the kind mediation of Mrs. F. M. Lindeman-Torgo, Utrecht, I received a sea-grass sample from South America. This appeared to consist of an undescribed species of Halodule. I am indebted to Dr. R. C. Bakhuizen van den Brink, Leyden, for rendering the diagnosis of this species into Latin.