Amphipods of the family Talitridae form an important part of the cryptozoa of Tasmanian forests. The terrestrial amphipod fauna of the Tasmanian mainland consists of fifteen species. The previously widely used grouping of land amphipods into the genera Orchestia and Talitrus is considered unsatisfactory and consequently a number of genera are created to receive the Tasmanian species. Three new genera, Neorchestia, Orchestiella and Tasmanorchestia, are described, and Mysticotalitrus, Arcitalitrus and Keratroides are raised to generic status. Twelve new species, Austrotroides longicornis, A. leptomerus, A. maritimus, Neorchestia plicibrancha, Mysticotalitrus cryptus, Arcitalitrus bassianus, Keratroides albidus, K. rex, K. pyrensis, Orchestiella neambulans, O. quasimodo and Tasmanorchestia annulata, are described. Mysticotalitrus tasmaniae is redescribed, and a description of the male is given. Keratroides vulgaris and K. angulosus are also recorded from Tasmania, and Protaustrotroides victoriae from King Island. Talitrus assimilis is considered a doubtful species. Among the Tasmanian fauna (excluding P. victoriae), four of the seven genera, but only one of the fifteen species also occurs on the Australian mainland. Examination of geological and paleoclimatic data suggests that this is due to the conditions which prevailed on the Bassian isthmus during Tertiary and late Quaternary times.