Nineteen new species and four forms in open nomenclature of Pithonella, here included in the incertae sedis family Calcisphaerulidae, are described from Upper Jurassic, Lower and Upper Cretaceous sediments recovered from Sites 259, 260, 261, and 263 of Leg 27 in the Eastern Indian Ocean. One genus, Andriella, is proposed as new. Previously, specimens of Calcisphaerulidae, which have an average size of 40-120µ were described exclusively from thin sections of limestones. The specimens from the Leg 27 sections could be isolated from the soft sediments and be studied by SEM methods. This led to the recognition of much more detail in wall structure (outside, inside, and cross-section views) than was previously possible. Most specimens are spherical in shape, some more or less ovoid or distinctly elongate, all usually with an aperture. The walls are composed of one to three layers, consisting of calcite crystals of different size, shape, and arrangement. The systematic position is still uncertain, but there are some indications that the tests may represent a cyst stage, possibly of algae. The stratigraphic distribution of the individual Pithonella species described here is restricted. Once investigated by SEM methods in more complete and better dated sections, Calcisphaerulidae may well become valuable index fossils for the Jurassic and Cretaceous. taxa after Egger, 1906, and published until 1972, is shown in Table 1, which contains, arranged in chronological order, the original taxa of family, genus, and species rank.
