Moore, Raymond C., H. L. Strimple, R. O. Fay, N. Gary Lane, and James Sprinkle. “Part T, Echinodermata 2, Vol. 1-3, Ch. 5, P. 520 - 630”. Treatise on Invertebrate Paleontology (January 1, 1978). Accessed April 28, 2024. https://journals.ku.edu/InvertebratePaleo/article/view/5646.