Tanoblastus roemeri
Blastoid
Mississippian (Kinderhookian)
Chouteau Limestone
Sedalia, Montana, USA

Cute little 7mm blastoid.  Early Carboniferous.

Tanoblastus is a lesser-known genus of blastoid from the Carboniferous of North America.

Blastoids are an extinct group of echinoderms that appeared during the Ordovician and survived into the Permian with the last members among the victims of the end-Permian mass extinction.