Accurate taxonomy and descriptions of species are key to understanding biodiversity. The echinoid genus Tripneustes is an ecologically and commercially important taxon that includes the pan tropical Tripneustes gratilla and the recently described T. kermadecensis from Australia and New Zealand. Occurrence of T. kermadecensis along the coast of New South Wales was previously considered to indicate a range extension of the tropical T. gratilla. We used the Australian Museum collections to clarify the distributions of these two species in east Australia and in the process, we found potential senior type material for T. kermadecensis. These specimens (lot J1099) were described as Evichinus australiae by Tenison-Woods (1878) and assigned the type locality of Sydney Harbour. We undertook molecular and morphological analysis of these specimens to determine if synonymy of T. kermadecensis to T. australiae was appropriate. This included micro-computed tomography and molecular genetic analysis using the mitochondrial marker cytochrome oxidase subunit I (COI). This revealed that the COI sequence and morphology of Evichinus australiae matched that of Tripneustes kermadecensis. Thus, we synonymise T. kermadecensis with Evichinus australiae (Tension-Woods 1978).