Kesling RV, Durham JW, Macurda Jr. DB, Wanner J, Beaver HH, Ubaghs G, et al. Part S, Echinodermata 1, vol. 1 & 2 , Ch. 2, p. 86 - 267. InvertebratePaleo [Internet]. 1968 Jan. 1 [cited 2024 May 1];. Available from: https://journals.ku.edu/InvertebratePaleo/article/view/5635