Discusses species of Foraminifera of limited range which can be used as time markers from lower middle Eocene to uppermost Miocene in western Ecuador. The Foraminifera are useful for facies distinctions also. It is noted that the molluscan time-scale based on Ecuadorean-Peruvian faunas is not coincident with the foraminiferal time-scale of the Caribbean region for the Tertiary, necessitating care in making correlations.