Homogeneous Thalassia beds in back-reef flat (less than 1 m) and Discovery Bay (about 3 m) were sampled for 12 successive months in Jamaica, West Indies. Living foraminifera were enumerated in each of four monthly replicates consisting of 20 ml of sediment. At the sampling times, water temperature, sediment temperature, salinity, oxygen saturation, water pH, sediment pH, sediment median, sediment sorting, turbidity, particulate organic carbon, Thalassia weight, and weight percent silt plus clay were measured. In all, 18,644 individuals belonging to 143 species were picked, sorted, and identified. The back-reef flat habitat contained 7,745 individuals belonging to 115 species, while the Discovery Bay contained 10,899 individuals belonging to 117 species. Fisher's log-series fits the distribution of species abundances at both habitats well. The number of species, information function, and equitability are usually greater at Discovery Bay for individual 20 ml samples. A general linear model consisting of parameters for station differences, overall periodicity, interaction of station differences and overall periodicity, and environmental variables was constructed. The densities of the 19 most abundant species were statistically analyzed individually (univariate) and simultaneously (multivariate). Univariate analyses indicate six species have significant station differences (95% level) and seven exhibit periodicity. The environmental variables are not significant for any of the species. Multivariate analyses indicate a significant difference between stations and an overall periodicity. As in the univariate analyses, environmental variables are not significant. The results suggest that in tropical habitats changes in species densities are regulated biotically. The new species Ammonia jacksoni, Elphidium norvangi, Fissurina goreaui, Discorbinella minuta, Glabratella altispira and G. compressa are described. Taxonomic remarks are presented for most of the species.