The writer has recently had the privilege of assisting in the revision of a glossary of the nomenclature of petrology. Certain observations were made bearing on the validity, on the mode of establishment, and on the applicability of many rock names in the literature during the course of this work. It is perhaps not generally realized how many varying reasons have been advanced by different authors for proposing a new rock name. An examination of the literature of petrology has shown that the bases of proposal have been greatly diversified. The reasons and arguments set forth, in certain individual but highly typical instances, seem to have been somewhat inadequately integrated with petrologic systems. The more specious names seem to have been advanced without reference to any system or standards whatever. But it may be stated that most authors, at the time of proposal, seem to have been fully aware of their responsibility. Many writers have been extremely diffident about coining a new rock name, but have eventually given way, as the multitude of igneous rock names indicates.