[Foraminifera] Each of the series of more or less spherical structures or sections of a foraminiferal shell; the initial chamber is the proloculus.

(Fo5a)
(Fo5b)
(Fo5e)
(Fo5g)

[Radiolaria Polycystina] In Nassellaria: one of the several sections into which the cephalis of the Nassellaria can be divided (see antecephalic, lateral, eucephalic and postcefalic chambers). See also central chamber.