1	Axis horny, with a chambered, hollow, soft central chord	2
–	Axis not horny, but is a solid axis, with no soft, central, hollow core	Suborder Calcaxonia, Part III
2	Axis purely horny, composed of scleroprotein, without any calcareous deposits	3
–	Axis horny, but some calcareous material may be present in some forms; hollow, horny, soft-chambered central chord is wide; there is a peripheral zone of hollow horny spaces containing calcareous material; cortex is thick, with an inner and outer layer, formed by systematic longitudinal canals; polyps retractile into prominent calyces	Family Plexauridae, Parts II & III
3	Axis perforated by a wide, cross-chambered central chord; cortex thin; polyps not retractile; sclerites spikey and conspicuous	Family Acanthogorgiidae, this part
–	Distinct hollow, horny, soft-chambered central chord that perforates axis is narrow; axial cortex surrounding the core is very dense; polyps fully retractile, into calyces	Family Gorgoniidae, Part II