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RDTALIDACEAE

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Originally appearing in Volume V10, Page 636 of the 1911 Encyclopedia Britannica.
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RDTALIDACEAE .—Shells vitreous, finely perforate; walls thick, often See also:

double, but without an intermediate party-layer traversed by canals; See also:form usually See also:spiral or trochoid. Discorbina (See also:Parker & See also:Jones) (fig. 4, 16) ; Planorbulina (d'See also:Orb.) (fig. 4, 17); Rotalia• (See also:tarok.) (See also:figs. 23, 1, 2; 7, 2s); Calcarina (d b.) (fig. 23, 10); Polytrema (Risso 23, 9). b sections showing dimorphism. (From See also:Lister.) a, Megalospheric See also:shell X 5o, showing See also:uniform growth, biloculine throughout. b, Microspheric shell X 90, showing multiform growth, quinqueloculine at first, and then multiform. XI. NUMMULINIDACEAE.—AS in. Rotalidaceae, but with a thicker finely perforated shell, often well See also:developed, and a supplementary See also:skeleton traversed by branching canals as an additional party-See also:wall between the proper chamber-walls.

Nonionina (d'Orb.) (fig. 4, 19) Fusiu- Tina (See also:

Fischer) (fig. 20) ; Polystomella (Lamk.) (figs. 4, 16; 8); Operculina (d'Orb.) (fig. 9); Heterostegina•(d'Orb.) (fig. 16) ; Cycloclypeus (Carptr.) (fig. flagellate gametes. nuclei of megalospheric form. 15); Nummulites (Lamk.) (figs. to, II, Conjugation, [zygote. 3, Nuclei. 12, 13, 14). Microspheric individual produced from 4, Nuclei in multiple See also:division. "Eozoon canadense," described as a See also:species of this The same resolved itself into pseudo- 5, Chromidia derived from 4. See also:order by J. W.

See also:

Dawson and See also:Carpenter, has been pronounced by a See also:series of enquirers, most of whom chamber; Cornuspira (See also:Schultze) (fig. 3); Miliola (Lamk.), started with a belief in its organic structure, to be merely a comincluding as subgenera Spiroloculina (d'Orb.) (figs. 3 and plea See also:mineral See also:concretion in ophicalcite, a See also:rock composed of an 22) ; Triloculina (d'Orb.) (fig. 3) ; Biloculina (d'Orb.) admixture of silicates (mostly See also:serpentine and See also:pyroxene) and (fig. 3) ; Uniloculina (d'Orb.) ; Quinqueloculina (d'Orb.) ; See also:calcite. Peneroplis (See also:Montfort) (figs. 22, 3; 3), with form Dendritina (fig. 4, 1) ; Orbiculina (Lamk.) (fig. 6-8) ; Orbitolites (Lamk.) (figs. 5, 6); Vertebralina (d'Orb.) (fig. 22); Squamulina (Sch.) (fig. 22); Calcituba (Schaudinn).

VI. TEXTULARIADACEAE.—Shells perforate, vitreous or (in the larger forms) arenaceous, in two or three alternating ranks (distichous or tristichous). Textularia (Defrance) (fig. 21). Modified from F. Schaudinn, in See also:

Lang's Zoologie. A, See also:Young megalospheric individual. podiospores which are growing into B, Adult decalcified. new megalospheric individuals. C, Later See also:stage, resolving itself into two 1, See also:Principal See also:nucleus, and 2, subsidiary D, E, F, See also:Distribution in See also:Vertical Space.—Owing to their lack of See also:organs for active locomotion the See also:Foraminifera are all crawling or attached, with the exception of a few genera (very See also:rich in species, however) which See also:float near the See also:surface of the ocean, constituting See also:part of the pelagic See also:plankton (q.v.). Thus the See also:majority are littoral or deep-See also:sea, sometimes attached to other bodies or even burrowing in the tests of other Foraminifera; most of the fresh-See also:water forms are sapropelic, inhabiting the layer of organic debris at the surface of the bottom mud ditches of pools, ponds and lakes. The deep-sea species below a certain See also:depth cannot possess a calcareous shell, for this would be dissolved; and it is in these that we find limesalts sometimes replaced by See also:silica. The pelagic floating genera are also specially modified. Their shell is either thin or extended many times by See also:long slender tapering spines, and the See also:protoplasm outside has the same See also:character as that of the See also:Radiolaria (q.v.), being differentiated into jelly containing enormous vacuoles and traversed by reticulate strands of granular protoplasm.

These coalesce into a peripheral See also:

zone from which protrude the pseudo-in See also:glauconite (a See also:green ferrous silicate, whose See also:composition has not yet been accurately determined) are, however, frequently See also:left. Glauconitic casts of perforate shells, notably See also:Globigerina, have been found in See also:Lower See also:Cambrian (e.g. Hollybush See also:Sandstone), and the shells themselves in Siberian limestones of that See also:age. It is only when we pass into the See also:Silurian See also:Wenlock See also:limestone that sandy shells make their See also:appearance. Above this See also:horizon Foraminifera are more abundant as constituents, partial or principal of calcareous rocks, the genus Endothyra being indeed almost confined to Carboniferous beds. The genus Fusulina (fig. 20) and Saccammina (fig. 19) give their names (from their a, Exterior of Saccammina. f, Nautiloid Lituola, exterior. b, The same laid open. g Chambered interior. c, Portion of test more highly h, Portion of labyrinthic cham- magnified. ber wall, showing component d, Pilulina. [magnified. See also:sand-grains. e, Portion of test more highly pods, here rather radiate than reticulate.

Most genera and most species are See also:

cosmopolitan; but See also:local See also:differences are often marked. Foraminifera abound in the See also:shore sands and the crevices of See also:coral reefs. The membranous shelled forms decay without leaving traces. The sandy or calcareous shells of dead Foraminifera constitute a large proportion of littoral sand, both below and above See also:tide marks; and, as shown in the See also:boring .on Funafuti, enter largely into the constituents of coral rock. They may accumulate in the mud of the bottom to constitute Foraminiferal See also:ooze. The source of these shells in the latter See also:case is double: (1) shells of bottom-dwellers accumulate on the spot; (2) shells of dead plankton forms sink down in a continuous shower, to form a layer at the bottom of the ocean, during which See also:process the spines are dissolved by the sea-water. Thus is formed an ooze known as " Globigerina-ooze," being formed largely of that genus and its ally Hastigerina; below 3000 fathoms even the tests themselves are dissolved. Casts of their bodies respective abundance) to two limestones of the Carboniferous series. Porcellanous shells become abundant only from the See also:Lias upwards. The glauconitic grains of the See also:Greensand formations are chiefly foraminiferal casts. See also:Chalk is well known to consist largely of foraminiferal shells, mostly vitreous, like the See also:north See also:Atlantic globigerina ooze. In the Maestricht chalk more littoral conditions prevailed, and we find such large-sized species as Orbitoides (vitreous) and Orbitolites (porcellanous; figs.

5, 6), &c. In the See also:

Eocene See also:Tertiaries the Calcaire Grossier of the See also:Paris See also:basin is mainly composed of Miliolid forms. Nummulites occur in See also:English beds and in the Paris basin; but the See also:great beds of these, forming See also:reef-like masses of limestone, occur farther See also:south, extending from the See also:Pyrenees through the See also:southern and eastern See also:Alps to See also:Egypt, See also:Sinai, and on to north See also:India. The See also:peculiar structure occurring in the Lower Laurentian limestone, as well as other limestones of Archean age described as a Nummulitaceous genus, " Eozoon," by Carpenter and Dawson, and abundantly illustrated in the 9th edition of his See also:encyclopaedia, is now universally regarded as of inorganic origin. " Looking r, Spirolxulina planulata, See also:Lamarck, showing five "coils"; porcellanous. 2, Young See also:ditto, with shell dissolved and protoplasm stained so as to show the seven nuclei n. 3, Spiraling (Peneroplis); a sculptured imperfectly coiled shell; porcellanous. 4, Vertebralina, a See also:simple shell consisting of See also:chambers succeeding one another in a straight See also:line; porcellanous. 4, 6, Thurammitsa papillata, See also:Brady, a sandy form. 5 is broken open so as to show an inner chamber; See also:recent. X 25. 7, Haplophragmium canariensis. a sandy form; recent.

8, Nucleated reproductive bodies (bud-spores) of Haliphysema. p, Squamulina laevis, M. Schultze; X 40; a simple porcellanous Miliolide. ro, Protoplasmic core removed after treatment with weak chromic See also:

acid from the shell of Haliphysema tumanovitzii, See also:Bow. n, Vesicular nuclei, stained with haematoxylin. (After Lankester.) rr, Haliphysema tumanovitzii; X 25 diam.; living specimen, showing the wineglass-shaped shell built up of sand-grains and sponge-spicules, and the abundant protoplasm p, issuing from the mouth of the shell and spreading partly over its projecting constituents. rz, Shell of Astrorhiza limicala, Sand.; X 'y; showing the branching of the test on some of the rays usually broken away in preserved specimens (See also:original). 13, See also:Section of the shell of bfarsipella, showing thick walls built of sand-grains.FIG. 23.—Perforata. z, Spiral arrangement of simple chambers of a Reticularian shell, as in small Rotalia. 2, Ditto, with double septal walls, and supplemental shell-substance (shaded), as in large Rotalia. 3, See also:Diagram to show the mode in which successively-formed chambers may completely embrace their predecessors, as in Frondicularia. 4, Diagram of a simple straight series of non-embracing chambers, as in Nodo. saris. 5, Hasligerina murrayi, Wyv.

See also:

Thomson. a. Bubbly (vacuolated) protoplasm, en-closing b, the perforated Globigerina-like shell (conf. central See also:capsule of Radiolaria). From the peripheral protoplasm project, not only See also:fine pseudopodia, but hollow spines of calcareous See also:matter, which are set on the shell, and have an See also:axis of active protoplasm. Pelagic; See also:drawn in the living See also:state. 6, Globigerina bulloides, d'Orb., showing the punctiform perforations of the shell and the See also:main See also:aperture. 7, Fragment of the shell of Globigerina, seen from within, and highly magnified. a, Fine perforations in the inner shell substances; b, See also:outer (secondary) shell substance. Two coarser perforations are seen in section, and one lying among the smaller. 8, Orbulina universa, d'Orb. Pelagic example, with adherent radiating calcareous snipes (hollow), and internally a small Globigerina shell. It is probably a develop-See also:mental phase of Globigerina. a, Orbulina shell; b, Globigerina shell. 9, Polytrema miniaceum, Lin.; x 12. Mediterranean.

Example of a branched adherent calcareous perforate Recticularian. so, Calcarina spengleri, Gmel.; X so. See also:

Tertiary, See also:Sicily. Shell dissected so as to show the spiral arrangement of the chambers, and the copious secondary shell substance. See also:a2, a3, a+, Chambers of three successive coils in section, showing the thin See also:primary wall (finely tubulate) of each; b, b, b, b, perforate surfaces of the primary wall of four tiers of chambers, from which the secondary shell substance has been cleared away; c', c', secondary or intermediate shell substance in section, showing coarse canals; d, section of secondary shell substance at right angles to c'; e, tubercles of secondary shell sub-stance on the surface; f, /, See also:club-like processes of secondary shell substance. at the almost universal See also:diffusion of existing Foraminifera and the continuous See also:accumulation of their shells over vast areas of the ocean-bottom, they are certainly doing more than any See also:ether See also:group of organisms to See also:separate carbonate of See also:lime from its See also:solution in sea-water, so as to restore to the solid crust of the See also:earth what is being continuously withdrawn from it by solution of the calcareous materials of the See also:land above sea-level." (E. R. Lankester, "See also:Protozoa," Ency. Brit. 9th ed.) See also:Historical.—The Foraminifera were discovered as we have seen by A. d'See also:Orbigny. C. E. See also:Ehrenberg added a large number of species, but it was to F.

Dujardin in 1835 that we owe the recognition of their true zoological position and the characters of the living See also:

animal. W. B. Carpenter and W. C. See also:Williamson in See also:England contributed largely to the study of the shell, the latter being the first to See also:call See also:attention to its multiform character in the development'of a single species, and to utilize the method of thin sections, which has proved so fertile in results. W. K. Parker and H. B. Brady, separately, and in collaboration, described an enormous number of forms .in a series of papers, as well as in the monograph by the latter of the Foraminifera of the " Challenger " expedition. Munier-Chalmas and Schlumberger brought out the fact of dimorphism in the group, which was later elucidated and incorporated in the full cytological study of the See also:life-See also:cycle of Foraminifera by J.

J. Lister and F. Schaudinn, independently, but with concurrent results. Appendix.—The XENOPHYOPHORIDAE are asmallgroup of bottom-dwelling See also:

Sarcodina which show a certain resemblance to arenaceous Foraminifera, though observations in the living state show that the character of the pseudopodia is lacking. The multinucleate protoplasm is contained in branching tubes, aggregated into masses of definite form, bounded by a See also:common wall of See also:foreign bodies (sponge spicules, &c.) cemented into a membrane. The cytoplasm contains granules of BaSO4 and pellets of faecal matter. All that is known of See also:reproduction is the See also:resolution of the pellets into uninucleate cells. (F. E. Schultze. Wissenschaftliche Ergebnisse der deutschen Tiefsee-Expedition, vol. xi., 1905, pt. 1.) (M.

End of Article: RDTALIDACEAE

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