Figure 60: Surface of attachment with supplementary apertures in Planorbulina mediterranensis d'
A: Free surface with apertures in subperipheral position. SEM graph. B: Equatorial section showing the nepionic, keeled spiral chambers followed by early chamberlet cycles with their oblique foramina and supplementary apertures where the section passes immediately below or within the attached chamber walls. Note the straight septa between the proconch and the two following chambers forming together a triconch. Transmitted light micrograph. C: Detail of surface of attachment with its tiny supplementary apertures in sutural position. Note the keeled nepiont. SEM graph.
a: aperture; f: foramen; k: keel of the nepiont; p: pore; pr: proloculus; sa: supplementary aperture.