Biochemical and morphological analyses show that two species in the Perinereis nuntia group occur in south-eastern Australia. The two species are distinguished by fixed differences at 4 of 8 enzyme loci, by non-overlapping ranges of paragnath counts and by qualitative differences in the types of paragnaths present. Previously, all material from south-eastern Australia had been referred to a single species, Perinereis nuntia, with two nominal varieties: P. nuntia vallata and P. nuntia brevicirris. Analysis of intraspecific variation shows that these varieties have no taxonomic significance. Differences between populations, especially those from markedly different sediments, exaggerate intraspecific variation in paragnath counts. Size related variation of paragnath counts is relatively unimportant.