HemipneustidaeHemipneustidae is an extinct family of sea urchins.GeneraHemipneustes L. Agassiz, 1835 †Medjesia Jeffery, 1997 †Opisopneustes Gauthier, 1889 †Plesiohemipneustes Smith & Wright, 2003 †Toxopatagus Pomel, 1883 †