Despite the fact that outcrops on the ocean bottom cannot be observed, it is often possible to make meaningful inferences about age relationships of Mid-Atlantic Ridge sediments by paleontologic methods. Data are briefly reviewed here to illustrate the utility of these methods. While data are still few, the inferred age relationships are in general agreement with the models of ridge development recently proposed by van Andel (1968). The pattern of inferred ages suggests an early, active phase of development with tectonism and volcanism prior to late Miocene, followed by a period of quiescence with pelagic deposition during late Miocene and Pliocene, and a final, late eruptive phase, perhaps occurring as late as the Quaternary.