Type locality of Trimma corerefum Uchelbeluu Reef (aka the Short Drop-off), SE of Koror Island. Confined to sheltered outer reefs in the central one-third of the main archipelago, from off Ulong Island in the south-west to Uchelbeluu Reef in the north-east. No specimens were caught to the South West Islands of Palau or any other localities in the main islands (Ref. 109919).