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The trilobite spans 146 meters from cephalon to pygidium, or head to tail, and is carved into the shape of a spiny Ceraurus trilobite instead of the plainer state fossil, Calymene.

The trilobite spans 146 meters from cephalon to pygidium, or head to tail, and is carved into the shape of a spiny Ceraurus trilobite instead of the plainer state fossil, Calymene.

“This is part of his thorax. And we have a thoracic vertebrae here. And at the end here, they call it the pygidium. I call it the trilobutt.”

Seen from above, it presents three divisions from front to rear:—first, a cephalic shield or head-piece; secondly, a thorax, divided into several segments movable upon each other; and thirdly, a tail-piece or pygidium, which, when brought against the head by the rolling up of the body segments, effectually covers the lower parts.

Squames: the flattened, fimbriated or spine-like marginal processes of the pygidium in Diaspinae, other than the lobes and true spines: = "plates," of Comst.; or "scaly hairs" of Maskell.