The Echinoid Directory

Fellaster Durham, 1955, p. 125

Diagnostic Features	Test with thin, sharp margin; slightly indented at ambulacral midpoints. Base flat, upper surface convex. Apical disc with 4 gonopores. Peripheral buttressing in the form of concentric walls around outer part of test only. Petals very broad and widely open distally. Pore pairs in petals conjugate. Alternating primary and demiplate throughout. All interambulacra disjunct orally; separated by a single pair of ambulacral plates. These ambulacral plates distinctly larger than other plates on oral surface. Basicoronal circlet pentagonal with angles formed by interambulacral plates. Two or three pairs of post-basicoronal interambulacral plates on oral surface. Periproct on aboral surface immediately adjacent to margin; opening bounded by third and fourth pairs of post-basicoronal interambulacral plates. Food grooves comprising simple perradial trunks only; extending aborally to the apex. No channel running from periproct to basicoronal plates on oral surface. Pedicellariae bivalved. Ambulacral tubercles and pores arranged linearly, forming combed areas. Combed areas well developed on both oral and aboral surfaces.
Distribution	?Oligocene, Pliocene to Recent of Australia and New Zealand.
Name gender	masculine
Type	Arachnoides zealandiae Gray, 1855, by original designation.
Species Included	F. zealandiae (Gray, 1855); Plio-Pleistocene to Recent, New Zealand F. incisa (Tate, 1893); Pliocene, Australia.
Classification and/or Status	Clypeasteroida; Clypeasterina; Arachnoididae. Presumed monophyletic.
Remarks	Differs from Monostychia and Ammotrophus in having an aboral periproct. Differs from Arachnoides in having no naked furrow running from the periproct to basicoronal plates and in having just a single pair of ambulacral plates separating the basicoronals from the first post-basicoronal interambualcrals. The Oligocene occurrence is cited in Durham (1966 Treatise on Invertebrate Paleontology), but it is not stated on what this is based. Mortensen, T. 1948. A Monograph of the Echinoidea IV.2 Clypeasteroida. C. A. Reitzel, Copenhagen. J. W. Durham 1955. Classification of clypeasteroid echinoids. University of California Publications in Geological Sciences 31(4), 73-198. Foster, R.J. & Philip, G.M. 1980. Some Australian late Cenozoic echinoids. Proceedings of the Royal Society of Victoria 91, 155-160.