The wee regular echinoid pictured below is Arbacina monilis from the Eocene near Nyirád, Hungary. I received them as part of an exchange with a collector in Hungary. The fossils have a bit of matrix on them still but you can clearly see the tubercles (the round bumps that the spines attach to). The fossils are from the Badenian stage of the Miocene which corresponds to the Langhian stage of the ICS).
Thanks to Karoly for the fossils!