Differs from Holectypus in having the periproct removed from the peristome and separated by four to six plates.
Vadet, A., Nicolleau, P. & Pineau, J.P. 1998. Echinides du Callovien de la Sarthe et de l'Orne II-B: Les echinides irreguliers: Description. Memoires de la Societe Academique du Boulonnais, Serie Histoire Naturelle 19, 1-128, pls 1-40.
Barras, C. G. 2006. British Jurassic irregular echinoids. Monograph of the Palaeontographical Society no. 625 (part of volume 159 for 2005), 1-168, pls 1-14.