A systematic revision of the so-called orbitoid foraminifera and allied forms, together with some three-layered types among the Nummulitidae, Pellatispiridae, and Orbitolitidae. Juvenile characters and the presence or absence of a canal system are considered important criteria for classification. Two new subfamilies, Pseudorbitoidinae and Pseudorbitellinae, are added to the Pseudorbitoididae, and Pseudorbitella americana n.g. n.sp. is described.

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