Kier, P. M., J. Wyatt Durham, Carol D. Wagner, and A. G. Fischer. 1966. “Part U, Echinodermata 3, Vol. 1 & 2, Ch. 5, p.492-670”. Treatise on Invertebrate Paleontology, January. https://doi.org/10.17161/dt.v0i0.5657.