Soritacea

The Soritacea are a group of miliolid benthic foraminifera with porcellaneous tests. They take on a variety of growth forms but typically have many chambers. Some soritids can grow over a centimeter across, huge for protists. All Soritacea keep algal endosymbionts, which may be what allows them to achieve such large sizes. Some species have red algal symbionts, some have green algal symbionts, and others dinoflagellate symbionts. These larger symbiont-bearing foraminifera are typically found in the oligotrophic waters of the tropics.

References

• Gudmundsson, G. (1994). "Phylogeny, ontogeny, and systematics of Recent Soritacea Ehrenberg 1839 (Foraminiferida)". Micropaleontology (The Micropaleontology Project, Inc.) 40 (2): 101–155. doi:10.2307/1485772. JSTOR 1485772.