Among the earliest races we have those remarkable forms, the
Trilobites, inhabiting the ancient ocean. These crustacea remotely
resemble the common wood-louse, and like that animal they had the power
of rolling themselves into a ball when attacked by an enemy. The eye of
the trilobite is a most remarkable organ; and in that of one species,
_Phacops caudatus_, not less than 250 lenses have been discovered. This
remarkable optical instrument indicates that these creatures lived
under similar conditions to those which surround the crustacea of the
present day.--_Hunt’s Poetry of Science._