Archaeocidaris wortheni

Mississippian

Saint Louis Limestone

Saint Louis, MO USA.

38mm echinoid with spines on 74mm matrix.

Carboniferous.

Archaeocidaris is a genus of echinoid from the Mississippian to Permian.  It’s known from sites in North America, Europe, and North Africa.

Back in the 90’s you would see specimens from Texas at shows rather regularly but you stopped seeing them by the early 2000’s.  These days, there are only occasional sightings at shows when one comes out of an old collection.