Species dominance in benthonic foraminifera, represented by percent of the assemblage composed of the single most abundant species, shows little change in observed range of values from shallow into deep-marine waters in 1005 samples from the Gulf of Mexico, Atlantic, and Arctic margins of North America. This finding contrasts with the model that species dominance is highest in shallow-marine environments and decreases offshore into deeper marine waters. Equitability, the relation of all species abundances within an assemblage, also shows little change between the values found in shallow-marine assemblages and those found in assemblages from deeper water environments. Equitability and dominance values found in 421 assemblages from Palaeocene, Eocene, Miocene, and Pleistocene strata of the Atlantic and E Gulf of Mexico coastal plains are similar to the modern values. -from Authors