Figure 22: Biumbilicate shell in Astrononion sp. from the Gulf of Aqaba, Red Sea, Recent. SEM graphs.
A: lateral view; B: apertural view; C: oblique view of dissected specimen showing structural details.
a: aperture; f: foramen; fo: folium; foa: foliar aperture; sf: septal face, covered by septal flap; up: umbilical plate; u: umbilicus, on both sides of the test.