The graticule described is for a polar aspect.
Meridians: Equally spaced semicircles from pole to pole, concave toward the west.
Parallels: Concentric circles.
Pole: The central pole is a point; the other pole is a bounding circle.
Symmetry: Radially about the center point.
This equal-area projection is a novelty map, usually centered at a pole, showing semicircular meridians in a pinwheel arrangement. Scale is correct along the meridians. This projection is not conformal.