We describe a second ichthyotoxic species within the genus Pfiesteria from the Albemarle-Pamlico and Chesapeake Estuaries of the eastern U.S., and will announce its soon-to-be-formal name in honor of a scientist who has contributed greatly to toxic dinoflagellate research. The second known toxic Pfiesteria species is polymorphic with a complex life cycle that includes an array of flagellated, amoeboid, and cyst stages. Its life cycle and behavior are, thus far, identical to that of Pfiesteria piscicida. This heterotrophic species can become mixotrophic with kleptochloroplasts, and it includes toxic, temporarily nontoxic, and never-toxic strains. The mesokaryotic zoospores (7-12 um) contain thin thecal plates arranged in a Kofoidian series of Po, cp, X, 4\', la, 6\'', 6c, 4s, 5\''\', 2\''\''. Their cysts are chrysophyte-like with organic scales and bracts; and they can also form temporary mucoid cysts. The eukaryotic, benthic amoeboid stages are morphologically filose to lobose, with reticulated cysts and length ranging thus far from 5 to 380 um. Anisogamous gametes fuse to form planozygotes with one transverse and two longitudinal flagella, which can become hypnozygotes. This species is distinguishable from P. piscicida both morphologically and genetically. Like P. piscicida, it shows strong preference for certain species of algal prey when fish are not available, and its toxicity varies depending on its history of access to fish prey.