This is a nice, spiny US trilobite. It is a complete Ceratonurus from Oklahoma. This type has very fine spines, compared to the Dicranurus found in the same formation. This specimen has great detail - it was extracted under a microscope. The stalked eyes are intact, and both genal spines and occipital 'horns' were prepared free-standing. Even the small barbs on the tail are preserved. The bug is also nicely centered on the naturally-edged matrix block.
It is very unusual to find a Ceratonurus this complete. It is a beautifully-prepared spiny trilobite for the price.