ABSTRACTAgardhiella coulteri(Harvey) Setchell (Solieriaceae) from the Pacific coast of North America is presently included in the circumscription ofNeoagardhiella baileyi(Kützing) Wynne&Taylor from the Atlantic and the Gulf of Mexico. Examination of fresh, liquid‐preserved and dried Pacific material has shown a different medullary and cystocarpic structure from specimens in eastern North America. The Pacific specimens are being removed fromN. baileyitoN. gaudichaudiicomb. nov., based onGigartina gaudichaudiiMontagne, the oldest available name for the Pacific material. Included inN. gaudichaudiiisAgardhiella mexicanaDawson from the Gulf of California (Mexico), and South American specimens formerly included in A.tenera(J. Agardh) Schmi