The Rotallida are an order in the kingdom Protista, phylum, subphylum or class Foraminifera, characterized by multilocular tests (shells) composed of bilammelar perforate hyaline lamellar calcite that may be optically radial or granular. Where the Foraminifera comprise a phylum, the class Rotalidia is equivalent to the order. Rotaliids are primarily oceanic benthos, although some are common in shallower estuarine waters. They also include many important fossils, such as the nummulitids.