The rocky intertidal fauna of south eastern Australia shows a change in community structure between the shores of Victoria and New South Wales. This may reflect the impact of a major biogeographic barrier formed by a remnant of a past palaeogeographical barrier in the Bass Strait region, the Bassian Isthmus, maintained at present by the presence of the 90 Mile Beach and the waning influence of the south flowing Eastern Australian Current and its convergence with the north flowing Bass Strait Cascade. The barrier is believed to have been intermittently in existence for millions of years and in its current form for at least the last 10000 years.  A small number of population genetic surveys of nuclear loci (allozymes and microsatellites) revealed that while some species show a clear division into northern and southern populations separated by the barrier others do not. Nuclear genetic data may, however, mask the relatively recent separation of lineages. Here we use mtDNA COI gene sequence information in a more sensitive test of the assumption that species showing little differentiation truly form a single panmictic population and to determine if life-history is a good predictor of dispersal across the barrier.