The spines are rather similar in form to those of Nortonechinus, being only a little more slender and less distally flattened. Should the test turn out to be identical in the two genera then they are best synonymized. As no test plates are known for Xenocidaris I prefer to retain the better known Nortonechinus and treat Xenocidaris as a nomen dubium.
Schultze, L. 1866. Monographie der Echinodermen des Eifler Kalkes. Denkschr. Kais. Akad. Wiss. Wien, Math.-Naturwis. Cl. 26, 113-230.
Mailleaux, E. 1940. Les echinodermes du Frasnien de la Belgique, Memoires de la Musee Royal d'Histoire Naturelle de Belgique 92, 1-46, pls 1-3.