The triploid (3x=2n=33) hybrid lycophyte Isoetes echinospora × septentrionalis has had a tangled nomenclatural history, largely due to taxonomic confusion surrounding putative parent I. septentrionalis (I. riparia, p.p.). Lectotypification of potential 19^thcentury names is further complicated by the absence of clearly designated types and a failure of authorities to recognize the existence of Isoetes hybrids at that time. Re-examination of the protologue and lectotype of Isoetes dodgei, the name most recently applied to I. echinospora × septentrionalis, indicates that this indiscriminately employs characteristics of three taxa and cannot be unambiguously applied to any particular taxon. An older name can be applied to the hybrid, however, based on an unequivocal lectotype and a clear protologue. Accordingly, the recombination I. ×robusta (Engelm.) D. F. Brunton, comb. nov., is proposed.