Additional paired antennae may occur within the coronal surface, which is the seat of the sensory styles, of less complex structure, which occur in many genera.
- Coronal Section through the Pelvis, showing the relations of the bladder above, prostate and bulb below.
Thus at Cape Thorsden (7) in 1882-1883 the mean of a considerable number of observations made the angle between the two directions only 1° 7', the magnetic inclination being 80° 35', whilst the coronal centre had an altitude of 79° 55' and lay somewhat to the west of the magnetic meridian.
- Free medusae with rhopalia of the normal type; the exumbrella is divided by a circular, so-called coronal groove, into two parts, a central portion, which is conical, thimble-shaped, or domed in form, and a peripheral portion, the pedal zone, which bears the marginal lobes, tentacles and rhopalia; the pedal zone is subdivided into areas termed pedalia, from each of which arises a tentacle or rhopaliurn in the interspace between two adjacent lobes of the margin.
- Medusae with umbrella flattened or disk-like, without coronal groove; lips always prolonged into long oral arms. The most prolific and dominant group of the Scyphomedusae, containing two suborders; the Semaeostomae, in which the oral arms remain separate, and the Rhizostomeae, in FIG.