Acanthurus rackliffei, a Possible Hybrid Surgeon Fish (A. achilles x A. glaucopareius) from the Phoenix Islands

T HE published records of naturally occurring hybrids of freshwater fishes are very numerous; those of marine fishes are exceptionally few in number. In an unpublished review of hybridization in New World fishes, Robert Rush Miller advises me that only 5 marine hybrids have been reported (1954) in contrast to 129 freshwater crosses. Only one additional instance of hybridization in marine fishes has come to his attention since this list was prepared. The overwhelming majority of freshwater hybrids is reflected not only from our greater knowledge of American freshwater fishes and greater opportunity for sampling populations of freshwater habitats but probably also from an actual lower percentage of hybrids in the sea. Undoubtedly conditions are more favorable, in general, for hybridization of fishes in the freshwater environment than in the marine.'