when gerard krefft named the species in 1873, he intended to commemorate the man who first reported it to him, australian native police officer and amateur naturalist robert arthur johnstone (1843-1905). however, krefft made an error in writing the name, and for many years the species has been known as "c. johnsoni". recent studies of krefft's papers have determined the correct spelling of the name, and much of the literature has been updated to the correct usage. however, both versions still exist. according to the rules of the international code of zoological nomenclature, the epithet "johnstoni" (rather than the original "johnsoni") is correct.