Moore, Raymond C., H. L. Strimple, R. O. Fay, N. Gary Lane, and James Sprinkle. 1978. “Part T, Echinodermata 2, Vol. 1-3, Ch. 5, P. 520 - 630”. Treatise on Invertebrate Paleontology, January. https://doi.org/10.17161/dt.v0i0.5646.