Shell spherical, with large circular or roundish pores of unequal size, two to four times as broas as the bars. Ten to twelve pores in the half meridan of the shell. Margin of every porewith a coronal of six to nine short and acute spines, not longer htan half the diameter of the pores. No spines between the pores. Dimensions. -- Diameter of the shell 0.16 to 0.2, of the pores 0.02 to 0.03; length of the spines 0.008 to 0.012.