Carex lemmonii W. Boott is a widespread California endemic. Herbarium and field studies showed its extensive morphological variation included plants called Carex albida L. H. Bailey, previously considered endemic to Sonoma County, California. Due to extensive overlap, characters of the perigynium, achene, inflorescence, and foliage did not separate the two taxa. Carex albida becomes a synonym of the earlier name, Carex lemmonii, which has implications beyond nomenclature. Carex lemmonii is common and is not a conservation priority in California. When merged with Carex lemmonii, the only known natural population of Carex albida will no longer qualify for protection under federal and state endangered species legislation. A key and illustrations are provided for California species in Carex section Aulocystis Dumort.