Plagiochasma is an extinct echinoderm genus in the family Pygaulidae. Species includes: * Plagiochasma olfersii (L. Agassiz, 1836); Hauterivian, Early Cretaceous of France and Switzerland * Plagiochasma faringdonense (Wright, 1875); Lower Greensand, Upper Aptian, Early Cretaceous of UK * Plagiochasma cruciferum (Morton, 1830); Paleocene of Denmark, Belgium, The Netherlands, Trinidad and the United States. * Plagiochasma texanum Smith & Rader, 2009; Lower Albian, Texas, USA