(fig. 22), Pilulina (Carptr.) (fig. 19), Saccammina (Sars) (fig. 19), Rhabdammina (Sars), Botellina (Carptr.), Haliphysema (Bowerbank) (fig. 22).
IV. Lituolidaceae.—Shell arenaceous, usually fine-grained, definite and often polythalamic, recalling in structure calcareous forms. Lituola (Lamk.) (fig. 19), Endothyra (Phil.), Ammodiscus (Reuss), Loftusia (Brady), Haplophragmium (Reuss) (fig. 22), Thurammina (Brady) (fig. 22).
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| Modified from F. Schaudinn, in Lang’s Zoologie. |
| Fig. 17.—Life Cycle of Polystomella crispa. |
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A, Young megalospheric individual. B, Adult decalcified. C, Later stage, resolving itself into two flagellate gametes. D, Conjugation. E, Microspheric individual produced from zygote. F, The same resolved itself into pseudopodiospores which are growing 1, Principal nucleus, and 2, subsidiary nuclei of megalospheric form. 3, Nuclei. 4, Nuclei in multiple division. 5, Chromidia derived from 4. |
V. Miliolidaceae.—Shells porcellanous imperforate, almost invariably with a camptostyle leading from the embryonic chamber; Cornuspira (Schultze) (fig. 3); Miliola (Lamk.), including as subgenera Spiroloculina (d’Orb.) (figs. 3 and 22); Triloculina (d’Orb.) (fig. 3); Biloculina (d’Orb.) (fig. 3); Uniloculina (d’Orb.); Quinqueloculina (d’Orb.); Peneroplis (Montfort) (figs. 22, 3; 3), with form Dendritina (fig. 4, 1); Orbiculina (Lamk.) (fig. 3, 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).
VII. Cheilostomellaceae.—Shells vitreous, thin, the chambers doubling forwards and backwards as in Miliolidae. Cheilostomella (Reuss).
VIII. Lagenidaceae.—Shells vitreous, often sculptured, mono- or polythalamic, finely perforate; chambers flask-shaped, with a protruding or an inturned stylopyle; Lagena (Walker & Boys) (fig. 4, 9); Nodosaria (Lamk.) (figs. 23, 4; 4, 10); Polymorphina (d’Orb.) (fig. 4, 13); Cristellaria (Lamk.) (fig. 4, 11); Frondicularia (Def.) (fig. 23, 3).
IX. Globigerinidaceae.—Shells vitreous, coarsely perforated; chambers few spheroidal rapidly increasing in size; arranged in a trochoid or nautiloid spiral. Globigerina (Lamk.) (23, 6; 4, 12); Hastigerina (Wyville Thompson) (fig. 23, 5); Orbulina (d’Orb.) (fig. 23, 8).
X. Rotalidaceae.—Shells vitreous, finely perforate; walls thick, often double, but without an intermediate party-layer traversed by canals; form usually spiral or trochoid. Discorbina (Parker & Jones) (fig. 4, 15); Planorbulina (d’Orb.) (fig. 4, 17); Rotalia (Lamk.) (figs. 23, 1, 2; 7, 21); Calcarina (d’Orb.) (fig. 23, 10); Polytrema (Risso) (fig. 23, 9).
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Fig. 18.—Biloculina depressa d’Orb., transverse sections showing dimorphism. (From Lister.) a, Megalospheric shell × 50, showing uniform growth, biloculine throughout. b, Microspheric shell × 90, showing multiform growth, quinqueloculine at first, and then multiform. |
XI. Nummulinidaceae.—As in Rotalidaceae, but with a thicker finely perforated shell, often well developed, and a supplementary skeleton traversed by branching canals as an additional party-wall between the proper chamber-walls. Nonionina (d’Orb.) (fig. 4, 19); Fusulina (Fischer) (fig. 20); Polystomella (Lamk.) (figs. 4, 16; 8); Operculina (d’Orb.) (fig. 9); Heterostegina (d’Orb.) (fig. 16); Cycloclypeus (Carptr.) (fig. 15); Nummulites (Lamk.) (figs. 10, 11, 12, 13, 14).
“Eozoon canadense,” described as a species of this order by J. W. Dawson and Carpenter, has been pronounced by a series of enquirers, most of whom started with a belief in its organic structure, to be merely a complex mineral concretion in ophicalcite, a rock composed of an admixture of silicates (mostly serpentine and pyroxene) and calcite.
Distribution in Vertical Space.—Owing to their lack of organs for active locomotion the Foraminifera are all crawling or attached, with the exception of a few genera (very rich in species, however) which float near the surface of the ocean, constituting part of the pelagic plankton (q.v.). Thus the majority are littoral or deep-sea, sometimes attached to other bodies or even burrowing in the tests of other Foraminifera; most of the fresh-water forms are sapropelic, inhabiting the layer of organic
