Euproops danae
Pennsylvanian
Francis Creek Shale
Pit 11, Will Co.
Illinois, USA.

Fossils of Euproops danae are best known from the coal-bearing deposits of North America and Europe, especially environments associated with Carboniferous swamps, estuaries, and shallow freshwater or brackish habitats.
15mm horseshoe crab in 49mm paired concretion