Closest to Echinocrepis which also has an inframarginal periproct and no subanal fasciole, but differing from that taxon in having ambulacra I and V disjunct - separated by plates of interambulacra 1 and 4 which meet along the midline. It also has a very different outline.
Agassiz A. 1904. Reports on an exploration off the west coasts of Mexico, central and south America and off the Galapagos Islands. Memoirs of the Museum of Comparative Zoology at Harvard University 31.
Mortensen, T. 1907. Danish Ingolf Expedition 4(2) Echinoidea, part 2.
Mortensen, T. 1950. A Monograph of the Echinoidea. V.1. Spatangoida 1. C. A. Reitzel, Copenhagen.