Abstract

Three types of wall microstructure were found: walls of identical, nearly parallel calcite crystals perpendicular to test surface; walls of short, prominent crystals surrounded within the wall by finer crystals; and walls in which some crystals are elongated as spines and surrounded within the wall by finer crystals. These microstructures and the basic type of chamber coiling are utilized for recognition of four families: Globorotaliidae, with eleven genera in two subfamilies (Globorotaliinae and Candeininae), have trochoid tests whose walls consist of identical crystals; Hantkeninidae, with five genera in two subfamilies, are initially planispiral, and their walls have identical crystals; Catapsydracidae, with four genera, have walls of short, prominent crystals; and Globigerinidae, with thirteen genera, have walls in which some crystals are elongated into spines.

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