Key to the shallow water (<20 m) species of Pteraster in the Aleutian Islands.

1a Rays eight to eleven; body firm, relatively rigid; color in life yellow to orange with brown markings...... Pteraster octaster

1b Rays normally five.................................................................................... 2

2b Actinolateral membrane wide, extending to near or beyond ray edge............................................. 3

2a Actinolateral membrane narrow, only about half of ray width................................................... 4

3a Surface finely papillose; suboral spine trigonal; color in life uniformly white to orange............ Pteraster willsi sp. nov.

3b Supradorsal membrane wrinkled or convoluted; suboral spine cylindrical color in life gray or pale tan to orange.................................................................................................. Pteraster militaris

4a Surface firm, relatively rigid, reticulated; actinolateral membrane narrow, extending only about half way to edge of rays; suboral spine cylindrical; color pattern in life tessellated............................................ Pteraster tesselatus