Macurda, Jr., D. B., Roux, M., Strimple, H. L., Brower, J. C., Ubaughs, G., Lane, N. G., Meyer, D. L., Breimer, A., Rasmussen, H. W., & Moore, R. C. (1978). Part T, Echinodermata 2, vol. 1-3, ch. 2, p. 217 - 316. Treatise on Invertebrate Paleontology. https://doi.org/10.17161/dt.v0i0.5643