Page:Scientific results HMS Challenger vol 18 part 1.djvu/812

604 aggregated without any order, like the Acervulinida among the Foraminifera. In some cases also here the primordial chamber is a trizonal Larnacilla-shell, in other cases it is a simple, subspherical or lentelliptical shell.

The last family, the Phorticida, is formed of irregular, in which a lentelliptical trizonal Larnacilla-shell (as an inner medullary shell) is enveloped by an irregular, latticed, or spongy cortical shell. They can be regarded as abnormalities or irregular deformities of Larnacida or Pylonida.

The central capsule of the is originally lentelliptical and preserves this form, the "triaxial ellipsoid," in the greater number of genera. In some groups it follows the prevalent growth of the shell in the direction of one of the three dimensive axes, and becomes prolonged in this way. In many chambered forms (particularly Tholonida and Zonarida) the growing central capsule gets constricted, corresponding to the constrictions of the shell. In the Soreumida and Phorticida its form often becomes irregular. But in general for the greater number of the lentelliptical form of their central capsule is quite characteristic.