Daucus pusillus  American Wild Carrot
ANNUAL.  Plants short, up to 30 cm.  Leaves finely dissected, lacy.  Flowers tiny, white, in flat-topped heads.  Spiny seeds are more conspicuous than the flowers.  Common on disturbed ground.  Spermolepis echinata is similar but the flowers, leaves, and stems are larger, the plant is often shorter, and it is much less common.
FAMILY:  Apiaceae (Parsley Family)