1. Halodule wrightii Ascherson, Sitzungsber. Ges. Naturf., Freunde Berlin. 1868:19. 1868.
Diplanthera beaudettei Hartog; Halodule beaudettei (Hartog) Hartog
Rhizomes: internodes 0.5----4 cm; scales 4----10 mm. Leaves dark red-brown; sheath 1.5--6 cm ´ 1--2 mm; blade 5--20 cm ´ 0.3--1.5 mm, apex notched or with very prominent, acute median tooth; veins ending in teeth or not. Inflorescences solitary. Staminate flowers: peduncles 10--25 mm; distal anthers ca. 0.5 mm higher than the proximal. Pistillate flowers: styles lateral to terminal. Fruits ovoid to globose, 1.5--2 ´ 1.2--1.8 mm.
Flowering summer. Intertidal zone of marine waters with sandy or muddy substrates; -2--0 m; Ala., Fla., La., Miss., N.C. , Tex.; e Mexico; West Indies; Central America (Guatemala, Belize, Nicaragua); South America (Venezuela).
Halodule wrightii occupies the shallowest waters in the Gulf of Mexico. In fact, the plants are often exposed during low tides.
All Halodule along the North American coast have been considered to be H. beaudettei (C. den Hartog 1964, 1970; concepts accepted by D. S. Correll and H. B. Correll 1972 and R. K. Godfrey and J. W. Wooten 1979). A study of the morphology of Halodule in one large population in the northern Gulf of Mexico showed the leaf tips in one population to range from that of H. beaudettei to that of H. wrightii (R. C. Phillips 1967). A later study of the isozymes of the two morphologic types showed no difference between the two (C. McMillan 1991). I amWe are following both R. C. Phillips and C. McMillan in accepting one species of Halodule in the Gulf of Mexico, i.e., H. wrightii. Halodule beaudettei, therefore, is a synonym of H. wrightii.