Quotation from: The Gods of Mars

Written by: Edgar Rice Burroughs

She commenced calling in a low singsong voice that was half purr.
She continued this as we wound our tedious way through the maze of
subterranean passages and chambers.

Presently soft, padded feet sounded close behind us, and as I turned I
saw a pair of great, green eyes shining in the dark shadows at our
rear. From a diverging tunnel a sinuous, tawny form crept stealthily
toward us.