They could always understand and be understood.

If you can explain this, please do.

I daresay I could understand your explanation, though you could never understand mine.
So when the girl said, 'Who are you ?' everyone understood at once, and Anthea replied-- 'We are children--just like you.

Don't be frightened.

Won't you show us where you live ?' Jane put her face right into the Psammead's basket, and burrowed her mouth into its fur to whisper-- 'Is it safe?
Won't they eat us?
Are they cannibals ?' The Psammead shrugged its fur.
'Don't make your voice buzz like that, it tickles my ears,' it said rather crossly.