Rotaliida

The Rotallida are an order of 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.

In form, rotaliid tests are typically enrolled, but maybe reduced to biserial or uniserial, or may be encrusting with proliferated chambers. Chambers may be simple or subdivided by secondary partitions; the surface is smooth, papillate, costate, striate, or cancellate; the aperture is simple or with an internal toothplate, entosolenian tube, or hemicylindrical structure; it may have an internal canal or stolen systems.

Rotaliids are primarily oceanic benthos, although some are common in shallower estuarine waters. They also include many important fossils, such as the nummulitids.