ABSTRACT
Actinal intermediate plates almost flat, rectangular to polygonal in shape, smooth or with scattered granules; most plates surrounded by a series of small granules and bearing a prominent spine or tubercle. Mouth plates triangularly elongated with 4 to 6 oral spines similar to the furrow spines, and 1 to 2 slender prominent suboral spines. Papulae single, distributed all over the abactinal surface except on the lateral interradial areas of the disk and on the most distal part of arms; no marginal or actinal papulae. As already noted by previous authors, the genus Calliaster is related to the genus Hippasteria Gray, 1840. Their most marked differences concern both the number of furrow spines and the structure of the abactinal skeleton. In Hippasteria, secondary plates occur all over the abactinal skeleton, forming regular reticulated meshes, while in Calliaster these plates develop only in the center of the disk, forming a rather irregular network.
