Arrangement of chambers Cont'

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Lecture 5
Arrangement of chambers(Cont.)
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• Milioline Winding growth with two chambers to
  the whorl with the aperture alternately at one
  end and then at the other. The successive
  chambers are added at 144º to each other
  (quinqueloculine), 120º (triloculine) or 180º
  (biloculine).

Pyrgo
Quinqueloculina
Triloculina
Spiroloculina
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• Polymorphine The successive chambers spiral
  about the growth axis of the test, all the
  apertures pointing in the same direction.

Globulina gibba
Polymorphina
Guttulina
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• Mixed chamber arrangement
• Mixed or multiform growth, where the juvenile is
  different in arrangement from the adult chambers,
  is common and in some cases three different modes
  may be shown.
• -Planispiral to uncoiled uniserial, Astacolus.
• -Planispiral to biserial, Spiroplectammina.
• -Biserial to uniserial, Bigenerina.
• -Trochospiral to triserial, Eggerella.

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• -Triserial to biserial, Gaudryina.
• -Triserial to uniserial, Clavulina.
• -Trochospiral to annular conical, Patellina.
• -Planispiral to annular discoid, Archians.
• -Trochospiral or planispiral to annular complex,
  Orbitoides.

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Morphology of chambers and the aperture

• Chambers are spherical to flattened in shape.
• They are separated from each other by partitions
  (or septa) the suture of which are rectilinear,
  curved or winding.
• The last chamber communicates with the exterior
  through an aperture.
• The aperture may be simple, in this case taking
  the shape of a circle, a slit or a crescent or
  it may be radial or denderitic, sometimes at the
  top of a neck or partially covered by calcareous
  projections (tooth, valve, trematophore or
  tegillum).
• There may also be multiple apertures with several
  small orifices arranged in a raw (linear
  aperture) or randomly (cribrate aperture). Its
  position in relation to the chamber may be basal,
  terminal, sutural or peripheral.

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• The shape of the aperture may be
• Rounded
• Fissurine (elliptical)
• Toothed (simple or bifid)
• Straight slit
• Arched slit
• Denderitic
• Phialine
• Radiate
• Cribrate

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• The position of the aperture may be
• Terminal
• Subterminal
• Sutural (textularian)
• Areal
• Umbilical
• Interiomarginal
• Exteriomarginal
• Equatorial
• On the apertural face
• At the end of the tube
• Some modifications of the aperture
• Simple lip
• Crenulated lips
• Lateral flanges
• Apertural teeth

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Surface ornamentation,

• The surface of the test is it smooth or covered
  with striations, ribs, tubercules, spines, etc.
• The extranal surface of the test may bear spines
  (termed spinose), keels (carinate), rugae
  (rugose), fine striae (striate), coarse costae
  (costate), granules (granulate), or a reticulate
  sculpture.
• These features should be used with caution in
  distinguishing certain genera and species for
  they vary through ontogeny and with environment.

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The surface ornamentation of the test may
be -Costae, Ribs, striations. -Hispid (very fine
short and hair-like spines). -Spinose (provided
with very fine spines, generally
elongate). -Rugose (characterized by rough
ornamentation which may form ridges). -Nodose
(surface ornamented with small knobs). -Reticulate
(with a honey-comb like surface). -Beaded
(provided with ornamentation like a string of
beads). -Pitted (small, generally rounded
depressions in the surface of the wal. -Limbated
(bordered by or provided with a flat or raised
strip). -Keeled (marginal cord of the
periphery). -Carinae (the edges of the chambers
often bear projecting sharp keels). -Septal
bridges (retral processes). -Smooth.
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Sutures

• They are simple or limbate (underlined by a band
  of variable width).
• The sutures are of two types
• -Spiral suture division between different whorls
  of the test.
• -Intercameral suture division between the
  chambers themselves.
• It may be described as
• Depressed, Flush, raised, limbate and obscured by
  the cortex.
• Or may be
• Straight, arched or curved, grooved and
  reticulate.

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Periphery

• Periphery of the test is the outer margin of the
  test, termed as the axial periphery (as shown in
  the axial or periphery view) and the equatorial
  periphery (as shown in ventral or dorsal view).
• The axial periphery may be desribed as
• Rounded
• Acute
• Keeled (ridge-like thickening of the chamber
  wall, present on the periphery of the test.
• The equatorial periphery may be described as
• Lobulate
• Nonlobulate

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Umbilicus
Umbilicus is it vacant or occupied by one or
more granules. It is a central area where the
septal traces (sutures) meet. When the umbilicus
is completely filled with secondary material, it
is called umbo. If slightly filled, it is called
an umbilical plug. The test may be described
as Umbilicate test (with an umbilicus). -Monoumbi
licate as in Globigerina -Biumbilicate as in
Hantkenina and Hastigerina. Umbonate test (with
an umbo) Monoumbonate as in Rotalia
StreblusAmmonia Biumbonate as in Robolus
Elphidium
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