Astrophytum Artenschlüssel / key to the species
BRITTON, N. L.; ROSE, J. N. 1937 . Seite: 2. ed.: Vol.III; 182-185; Plate XXI, XXII Carnegie Inst. of Washington The Cactaceae - Descriptions and Illustrations of Plants of the Cactus Family

Spines wanting.
Plants globular to columnar; flowers 4 to 6 cm long.................................................1. A. myriostigma
Plants much depressed; flowers 3 cm long................................................................2. A. asterias

Spines present.
Spines flat, ribbon-like, hardly pungent.....................................................................3. A. capricorne
Spines subulate..........................................................................................................4. A. ornatum