A comparison is made between the late Neogene planktonic foraminiferal biostratigraphy of Italy and the Caribbean and Gulf of Mexico. In both regions the order of stratigraphic appearance of the species Globorotalia margaritae (= G. hirsuta auct.), G. aemiliana, G. crassacrotonensis, G. crassaformis, G. tosaensis, and G. truncatulinoides is closely comparable and provides a basis for interregional correlation of the Pliocene and early Pleistocene. The occurrence of G. margaritae defines the early Pliocene; the globorotaliid lineage of G. aemiliana ^rarr G. crassacrotonensis ^rarr G. crassaformis defines the middle Pliocene; and the appearance of G. tosaensis, G. truncatulinoides,

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and Sphaeroidinella dehiscens defines the very late Pliocene and early Pleistocene. Onset of climatic deterioration in both regions defines the base of the Pleistocene. In Italy the base of the Pleistocene corresponds to the arrival of the cold-water immigrant species Arctica islandica and Hyalinea balthica, whereas in the Caribbean and Gulf of Mexico climatic cooling was accompanied by either extinction or withdrawal of the warm-water Pliocene species Globoquadrina altispira, G. venezuelana, and Globorotalia menardii and the appearance of the cool-water immigrant species G. inflata. Paleobathymetric and physical evidence shows upward shallowing of facies in the very late Pliocene and early Pleistocene, which seemingly is indicative of and related to glacio-eustatic phenomena.

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