Coral Field Guide

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

Polyps not extended during daytime

Corallites very small (<5mm)

Each corallite look like a mini volcano	Cyphastrea serailia
The coral have round nodule or short branches	Porites aranetai
Coral surface typically smooth, sometimes colonies in helmet shape	Porites lutea