16.The beetles and their dung balls were then released in the centre of a circular arena made of flattened sand and enclosed by a featureless circular wall.
19.Telescopic observations show it to be a nearly featureless white disk, completely covered in a thick cloud layer, reflecting almost all of the sunlight that falls on it.
20.It's easy to get lost in the salt pans of Tunisia, these featureless plains in the desert where the ground is sometimes the blinding white color of salt.