Foraminifera

Collier's New Encyclopedia (1921)

an order of animals belonging to the sub-kingdom Protozoa, and the class RHIZOPODA (q. v.). The body is contained within a calcareous test or shell, which is polythalamous (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 foramina, or small apertures. Foraminifers are always of small size, and often indeed microscopic. With the exception of fresh and Gromia, which occurs both in salt water, they are exclusively marine, Sometimes their shells lls constitute sea sand. In the Atlantic, at a depth of 3,000 fathoms, there is an ooze composed almost entirely of Globigerinæ, which belong to this order; the stratum thus formed is a direct continuation of the white chalk deposit, having gone on apparently through the whole Tertiary period. Drs. Carpenter and Parker, and Prof. T. Rupert Jones have divided the Foraminifera thus: Sub-order I.-Imperforata. Families: (1) (1) Gromida, (2) Miliolida, (3) Lituolida. Sub-order II. - Perforata. Families: (1) Lagenida, (2) Globigerinida, and (3) Nummulinida. The exceedingly antique Eozoön of the Laurentian rocks, if organic, as it is generally believed to be, was apparently a foraminifer. Forms more unequivocal, some of them very like recent species, occur in the Silurian, the Carboniferous, and other strata. They are found through all the Secondary period, chalk being almost entirely composed of their cases. They increase in number and importance in the Tertiary. The nummulites of the Midde Eocene are foraminiferous animals.