Calochortus ambiguus  White Mariposa; False Sego Lily
PERENNIAL.  Cup-shaped flowers have three white petals that have a purple crescent at the base and are often washed with purple on the back.  Long stalk (to about 30 cm) has a few narrow, sharp pointed leaves.  Blooms in April-May.  In the Empires, uncommon on limestone in desert grassland after wet winters.
FAMILY:  Liliaceae (Lily Family)