Here is nice and well preserved Utah Trilobite of the species Modocia typicalis without matrix.
The Trilobite was may naturally weathered out of its original matrix.
In order to increase its retail value had the trilobite been artificiality mounted in a other piece of shale. Such manipulations are  usually not been told to the customers and they are very common on internet auction platforms.
Now this nice trilobite is in a authentic state again.
The misused matrix with a Ptychagnostus atavus on it is included for free.

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