FORAMINIFERA, an order of animals in the phylum Protozoa and the class Rhizopoda. The body is contained within a calcareous test or shell, which is many chambered. It may be cylindrical or spiral, or it may tend to the pyramidal form. The outer surface presents a punctate or dotted appearance, produced by the presence of very numerous small apertures, or ((foramina?' The chambers in some are per fectly distinct from others, though so aggre gated as to form a compound shell; in others they are connected with a funnel-like tube. The texture of the shell in one group is porcelain like, in another glassy. The inside of the shell has an extensile and contractile sarcode (pro toplasm) of a reddish or yellow color, which streams through the openings and thinly covers the outside. Foraminifers are always of small size, and often microscopic. With the exception of Gromia and one or two related genera which occur both in fresh and salt water, they are exclusively marine and many dwell only in the abysses. Sometimes their shells constitute sea
sand. In the Atlantic, at a depth of 3,000 fath oms, there is an ooze composed almost entirely of Globigeritue which belong to this order. See GLOBIGERINA.
The exceedingly antique Eozoon (q.v.) of the Laurentian rocks, if organic, as is generally believed, was apparently a foraminifer. Forms more unequivocal, some of them very like recent species, occur in the Silurian, the Carbonifer ous, and other strata. They are found through all the Secondary Period, chalk (q.v.) being almost entirely composed of their cases. They increase in number and importance in the Ter tiary. The flat, coin-shaped nummulites of the Middle Eocene form the principal bulk of great series of limestone rocks that furnish excellent building-stone. The type of the order has re mained wonderfully constant from the earliest times till now.