Elrathia marjuma Cambrian Trilobite

A truely fine example of this species. The Elrathia marjumi comes from the formation directly on top of the layer containing the common Elrathia kingii, and may be a direct descendant.

The differences are small. The main difference is two short stubby spines (comapred with E. kingii) on the pygidium, just below the last thorasic segment. But even in the closeup its hard to see. This species is found higher in the Cambrian strata, than the E. kingii, and the marjumi are found in matrix that is much harder than that of Kingi, making preparation much more difficult.