The Echinoid Directory

Homalocidaris Mortensen, 1928, p. 67

Diagnostic Features
  • Test low; relatively thin and fragile.
  • Apical disc and peristome slightly less than 50% test diameter; dicyclic; plates generally covered in tubercles. Ocular pores rimmed.
  • Interambulacra of relatively few plates (up to 7). Tubercles perforate and non-crenulate with strongly sunken, ovate areoles. Scrobicular circle not differentiated from other secondary tubercles; tubercle dominating plate with only narrow adradial and interradial bands of secondary tubercles. Areoles almost, but not quite, confluent.
  • Ambulacra distinctly sinuous. Pore-pairs very small and oblique, usually with the two pores coalesced by loss of the interporal partition. Primary and smaller secondary tubercle to each ambulacral plate. Pore zones not sunken.
  • No naked perradial or interradial zone or pits developed.
  • Peristome with relatively few ambulacral plates; interradial plates very few and present only distally.
  • Primary spines long, cylindrical, with short collar and distinct neck. Shaft smooth and unornamented.
  • Secondary spines simple.
Distribution Recent; Antarctica.
Name gender feminine
Type Austrocidaris gigantea Clark, 1925, p. 28, by original designation.
Species Included Only the type species.
Classification and/or Status Cidaroida, Ctenocidaridae.

Remarks The enlarged, almost confluent primary tubercles readily distinguish Homalocidaris from other ctenocidarids.

Mortensen, T. 1928. A monograph of the Echinoidea. 1, Cidaroidea. C. A. Reitzel, Copenhagen.