Invisible Birds

I am a trilobite.
Or, the hollow shape of a trilobite
Engraved, a prisoner in patterned shale.
I have become limestone.
I have become a picture in a science book,
An image clicking through a set of slides—
The State Fossil of Pennsylvania.
Is such fame, such reknown, a triumph?
Am I trampled in the mud? Crystallised
In a bituminous vein.