The Echinoid Directory

Rhynchocidaris Mortensen, 1909, p. 5

Diagnostic Features	Test low and rather thin-plated. Apical disc and peristome about 50% test diameter; more or less dicyclic; plates generally covered in tubercles. Ocular pores rimmed. Interambulacra of relatively few plates (up to 9). Tubercles perforate and non-crenulate with sunken areoles. Scrobicular circle not differentiated from other secondary tubercles; plate outside areole uniformly covered in secondary tubercles with no naked interradial zone. Ambulacra almost straight. Pore-pairs very small and highly oblique, the two pores separated by a narrow partition. The neural canal large and partially separated from the inner pore on adoral plates. Primary and smaller secondary tubercle to each ambulacral plate. Pore zones not sunken. No naked perradial zone or pits developed. Peristome with few series of ambulacral plates; non-ambulacral plates confined to outer zone. Primary spines long, cylindrical, with short collar and distinct neck. Shaft ornamented with irregular thorns and with dense and fine hairs in between. Secondary spines clavate, erect.
Distribution	Recent, Antarctic.
Name gender	feminine
Type	Rhynchocidaris triplopora Mortensen, 1909, p. 5, by original designation.
Species Included	Only the type species.
Classification and/or Status	Cidaroida; Ctenocidaridae. Monotypic.
Remarks	Distinguished from Ctenocidaris by having pore-pairs with the neural notch in the perradial pore of each pore-pair partially or completely separated as a distinct perforation. Mortensen, T. 1909. Echin. aus dem Deutsch. Sudpolar-Expedition 1901-1903. Deutsh. Sudpolar-Exped. 1901-1903, Band 2, p. 5 Mortensen, T. 1928. A monograph of the Echinoidea. 1, Cidaroidea. C. A. Reitzel, Copenhagen.