Detailed investigation of the essentially complete uppermost Miocene through Lower Pleistocene sequence in Deep Sea Drilling Project (DSDP) Hole 603C, western North Atlantic, has revealed the presence of the new dinoflagellate cyst species Lejeunecysta hatterasensis, Lejeunecysta interrupta, Corrudinium devernaliae, and Pyxidinopsis vesiculata, as well as the acritarchs Leiosphaeridia rockhallensis Head new species and Leffingwellia costata new genus and species. Independent magnetobiostratigraphic control of DSDP Hole 603C constrains the ranges of these new species. Lejeunecysta interrupta n. sp. appears to range no higher than lowermost Pliocene at 5.2 Ma, Pyxidinopsis vesiculata n. sp. has a range top at about 4.5 Ma in the Lower Pliocene, Corrudinium devernaliae n. sp. has a well-defined range of 4.7–4.1 Ma within the Lower Pliocene, and Leiosphaeridia rockhallensis n. sp. has a similarly well-defined range of 4.4–3.9 Ma within the Lower Pliocene. The presence of Leiosphaeridia rockhallensis n. sp. in the Ramsholt Member of the Coralline Crag Formation, eastern England, supports an Early Pliocene age for this member.