Measurements on vegetative and reproductive structures from plants of the genus Batophora J. Agardh were made. Plants possessed spherical or ovoid gametophores, corresponding to Batophora oerstedi and B. occidentalis species, respectively. Both species coexist in the Chetumal Bay estuarine system. The species present different vegetative and reproductive characteristics compared to Batophora species from other parts of the world. The two species have different positive relationships between gametophore area and number of gametangia, and between reproductive thalli distance and number of gametophores. Gamete release was assayed applying two treatments to gametangia. Gamete release was significantly greater in B. occidentalis than in B. oerstedi. Both species showed the highest percentage of gamete release at between 100 and 150 μmol m - 2 s - 1 radiation. Reproductive potential per plant was estimated in July 1999 to be similar for both species; however, the difference in the number of reproductive plants per unit area of the Bay provided a greater total reproductive potential for B. occidentalis than for B. oerstedi. The reproductive differences may permit the two Batophora species to coexist in sympatry in Chetumal Bay. The reddish-brown pigmentation of gametophores exhibited by both species invalidates the diagnosis of B. occidentalis var. largoensis, a variety that has been separated on the basis of its color.