Most trilobites grew to only three inches long, while a few reached as much as three feet long. This Calymene, celebra fossil fits nicely into the palm of a man’s hand. In life, it was a scavenger finding food on the ocean floor where it could easily burrow underneath the sand to hide from predators. Many of their fossils are often found rolled up in a defensive position. They were able to bend because their chiton exoskeletons were fitted with overlapping sections. Think of a roly-poly bug, or pill bug as some call it, it’s the same idea.
Trilobites, in general, had many life styles; some moved over the seabed as predators or scavengers, while others were filter feeders, yet some swam along the ocean strata feeding on plankton. Most were sluggish swimmers, while some varieties were designed precisely for speed and swam in the mid ocean ranges where more predators existed.
Trilobite means three lobes as you can depict from this illustration.