Figure 36: Development of chamberlet cycles from an auxiliary chamber in an early orbitoid, the Campanian Lepidorbitoides minima
A: stereograph of a megalospheric embryo consisting of a biconch (protoconch and deuteroconch) supplemented by a third chamber (auxiliary chamber) with a median and two lateral stolons. Successive growth stages coloured alternately in red and blue. Lamellation omitted. Schematic, not to scale. B: development of chamberlet cycles. Schema, not to scale. Inner lamella omitted, outer lamella alternating in white or plain black in successive growth stages. Axes of successive stolons form overcrossing spirals (arrows). Median stolons indicated by dotted arrows, lateral stolons by black arrows. C: Camera lucida drawing of a slightly oblique section of the equatorial main chamberlet layer of adult growth stage showing retrovert apertures and annular passages. D: stereograph of adult chamberlets of two successive cycles with their crosswise-oblique stolon axes, the annular passage and their retrovert stolons. Schematic, not to scale.
A: auxiliary chamber; D: deuteroconch; P: protoconch; X: closing chamberlet filling up the first chamberlet annulus; ap: annular passage; chl: chamberlet lumen; lst: lateral stolon; mst: median stolon; p: pores; rst: retrovert stolons; stax: crosswise-oblique stolon axes.