Distinguished from Eucidaris by is more fusiform spines with a more spinose ornament, and by having clearly conjugate pore-pairs. Phyllacanthus differs in having an enlarged madreporite and biserial pore-pairs on the outer part of the peristome. The type species has rather stouter and more fusiform spines than is typical of Prionocidaris, but little else distinguishes the two.
Agassiz, A. & Clark, H. L. 1907. Hawaiian and other Pacific Echini. Memoirs of the Museum of Comparative Zoology at Harvard University 34(1), 1-42, pls 1-42
Mortensen, T. 1928. A monograph of the Echinoidea. 1, Cidaroidea. C. A. Reitzel, Copenhagen.