What is the simple key to identify common coral species in this field guide?

Dichotomous Key in identifying twenty selected scleractinian corals within the Marine Parks in HK

Massive/Submassive/Encrusting form corals

Corals with polyps extended during daytime

Polyps very long and fleshy, with 24 tentacles	G.columna
Corals with hydnophores (small mound structures on coral surface)	H.exesa
Corallites tubular	G.fascicularis
Colonies are brownish purple with contrasting white corallite centre	L.purpurea