The Rotaliida are a large and abundant group of foraminifera

Foraminifera

The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...

ns. They are primarily oceanic benthos

Benthos

Benthos is the community of organisms which live on, in, or near the seabed, also known as the benthic zone. This community lives in or near marine sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths.Many organisms...

, although some are common in shallower waters such as estuarie

Estuary

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

s. They also include many important fossils, such as nummulite

Nummulite

thumb|left|250px|Fossil Nummulites in [[Urbasa]], [[Basque Country |Basque Country]]A nummulite is a large lenticular fossil, characterized by its numerous coils, subdivided by septa into chambers. They are the shells of the fossil and present-day marine protozoan Nummulites, a type of foraminiferan...

s. Rotaliids produce hyaline tests, in which the microscopic crystals may be oriented either radially (as in other forams) or obliquely.