Diagnosis: Shell nearly spherical, with 6 (seldom 7) strong radial spines equal to or somewhat longer than shell diameter, with whorl of 3 (sometimes 4) short, thick, slightly curved by-spines at the middle or nearer the base. Bases of spines with ring of 4 (seldom 3 or 5) elongate pores and a whorl of usually 8 long, thin by-spines, slightly curved at the distal ends of the radial spines. Shell wall with alveolar structure. Mouth large, triangular or more rounded, with 3 narrow spines, with 1 or 2 basal by-spines.
Diameter: 0.14-0.2 mm.