SUMMARYPulchrasphaera macronucleatagen. et sp. nov. was isolated from a sand dune on Dauphin Island, Alabama. The distinguishing attributes of the genus include a lobed and perforate parietal chloroplast, lack of pyrenoids, andProtosiphon‐type zoospores. The specific epithet calls attention to the unusually large nucleus, a character useful in distinguishingP. macronucleatafrom other spherical, zoospore producing members of the Chlorococcale