Arxiella lunata Ruscoe (1970) is not congeneric with the type species of Arxiella Papendorf (1967), A. terrestris Papendorf, for the latter species has solitary or catenate, obliquely cornute, uniseptate, hyaline or pale brown conidia produced from polyblastic conidiogenous cells, several of which are incorporated into a single conidiophore. Arxiella lunata is more closely related to Idriella on account of the polyblastic sympodial subhyaline conidiogenous cells with conidiogenesis restricted to the apices, and the presence of chlamydospores. The septate conidia are at variance with those of I. lunata but this feature is not considered to be of major significance in separating the genera. Since the epithet 'lunata' is preoccupied in Idriella, the species described by Ruscoe is provided with the following new name.
Idriella australiensis nom. nov. (not Arxiella lunata Ruscoe, Trans. Br. Mycol. Soc. 55(3): 507, 1970, non Idriella lunata Nelson & Wilhelm, 1956).