Phase G reported by Ohtani et al. [1997> and Kudoh et al. [1997a> is identical with the new phase D reported by Kuroda and Irifune [1998> and Yang et al. [1997>. However, there is ambiguity on existence of phase D defined by Liu [1987>. There are following possibilities on existence of Liu's phase D; (1) the product was a mixture of phase G and the other contaminant phases, (2) it really exists stably in different pressure and temperature conditions from those studied by our works, or (3) the phase is a metastable phase formed due to a short run duration and/or no sealing of water in the diamond anvil cell. Therefore, it is not appropriate to use the name phase D for the dense hydrous magnesium silicate phase G reported by us [Ohtani et al., 1997>. ¿ 1998 American Geophysical Union