just realised I did not fully answer your question.
E. irwini can be distinguished from the Cape York species (South Johnstone) by its eye color, the shape of the posterior carapace, plastron shape and a number of features on the skull. They also differ at 7% of allozymes. From the southern species (Burnett) by the reduced spiny projections of the carapace in E. irwini, Eye color, and a sweep of skull characters. Again they also differ at about 8% of allozymes.