Foraminifera

Foraminifera
SEM micrographs of four benthic foraminiferans (ventral view). Clockwise from top left: Ammonia beccarii, Elphidium excavatum clavatum, Buccella frigida, and Eggerella advena.
Scientific classification
Kingdom: Protista Phylum: Granuloreticulosa Class: Foraminifera
Orders
Allogromiida Carterinida Fusulinida - extinct Globigerinida Involutinida Lagenida Miliolida Robertinida Rotaliida Silicolocunida Spirillinida Textulariida

The Foraminifera are marine amoeboids with reticulating pseudopods, distinguished mainly by forming shells or tests. These are generally calcareous and multi-chambered, and vary greatly in form, from simple chains of compartments to spirals similar to snail or ammonite shells. The form of the test is the primary means by which they are classified. Foraminiferans are mostly benthic, and are among the most common marine protozoa. They tend to be relatively large, a few reaching over 10 cm in diameter. Several thousand species are known, some living and some as fossil shells. These are found from the Cambrian period onwards, and make up an important component of many marine sediments.