Micraster leskei
Echinoid
Late Cretaceous (Upper Turonian)
Rouen Chalk, Leskei biozone
Dieppe (76), France

42mm on 86mm chalk slab.

Micraster is a Late Cretaceous to Eocene genus of “heart urchin” known from various parts of the world.  Specimens from the chalk deposits of Europe are often especially excellent, having that full, inflated quality.

Here is a nice matrix specimen.