ABSTRACT. – As judged by its position in an SSU rRNA tree, a new algal class in the heterokonts has been recovered from a Bayesian phylogenetic analysis of 12 heterokont algal classes. The sequences were deposited in Genbank as raphidophytes, possibly because cells of these species resemble raphidophytes. A constrained tree placing them in the raphidiophytes yielded a significantly worse tree as determined by the Shimodaira-Hasegawa test (P = 0.0001). New efforts should be made to describe this class formally because cultures do exist for these microalgae.