Note: Farghaly (1980: 245–262), in his treatment of Udotea, resurrected the genus Rhipidosiphon Montagne (1842a: 14) and recognized three segregate genera: Decaisnella, Geppina, and Howella. The new generic names are invalid because their protologues lack Latin diagnoses and thus fail to satisfy Art. 36.2. The species of Udotea in this catalogue are distributed by Farghaly as follows: Udotea (U. argentea, U. flabellum); Decaisnella (U. indica, U. palmetta, U. papillosa); Geppina (U. wilsonii); and Rhipidosiphon (U. explanata, U. glaucescens, U. javensis, U. orientalis).
Udotea argentea Zanardini, 1858: 290 (type locality: Suez, Egypt).—A. Gepp & E. Gepp, 1908: 176–177.— A. Gepp & E. Gepp, 1909: 386–387.— A. Gepp & E. Gepp, 1911: 125, 126, 127, 143–144, pl. II: fig. 21; pl. III: fig. 22d; pl. VII: figs. 57, 58c, 59 ("forma typica'').— Børgesen, 1940: 60.— Børgesen, 1946: 42.— Børgesen, 1949a: 18–19, figs. 8, 9 ("var. typica'').— G. Davies, 1970: 117, 119, 121.— Logan & Cebulski, 1970: 32.— Pichon, 1978: 422.— Farghaly, 1980: 94, 259–260.— Huisman et al., 1990: 90.— Kendrick, Huisman, & Walker, 1990: 49.— M. Littler, D. Littler, & Titlyanov, 1991: 204, fig. 4J, tables 3, 4.— Kalugina-Gutnik, Perestenko, & Titlyanova, 1992: 24 (table 1).— Titlyanova, Perestenko, & Kalugina-Gutnik, 1992: 45.
Misapplied name (fide Børgesen, 1946: 40, 42):
Udotea flabellata.—Jadin, 1935: 157 (in part, one specimen being referred to an undescribed species of Avrainvillea).
INDIAN OCEAN DISTRIBUTION: Amirante Islands (St. Joseph Atoll), Australia, Cargados Carajos, Madagascar, Mauritius, Seychelles, Singapore.