These examples exhibit the characteristics of a large class of mountain masses or ranges. A geosynclinal accompanied by sedimentary depositions, and ending in a catastrophe of plications and solidification, are the essential steps, while metamorphism and igneous ejections are incidental results. The process is one that produces final stability in the mass and its annexation generally to the more stable part of the continent, though not stable against future oscillations of level of _wider range_, nor against denudation. It is apparent that in such a process of formation elevation by direct uplift of the underlying crust has no necessary place. The attending plications may make elevations on a vast scale and so also may the shoves upward along the lines of fracture, and crushing may sometimes add to the effect; but elevation from an upward movement of the downward bent crust is only an incidental concomitant, if it occur at all. We perceive thus where the truth lies in Professor Le Conte’s important principle. It should have in view alone _monogenetic_ mountains and these only _at the time of their making_. It will then read, plication and shovings along fractures being made more prominent than crushing: Plication, shoving along fractures and crushing are the true sources of the elevation that takes place _during the making_ of geosynclinal monogenetic mountains. And the statement of Professor Hall may be made right if we recognize the same distinction, and, also, reverse the order and causal relation of the two events, accumulation and subsidence; and so make it read: Regions of monogenetic mountains were, previous, and preparatory, to the making of the mountains, areas each of a slowly progressing geosynclinal, and, _consequently_, of thick accumulations of sediments. The prominence and importance in orography of the mountain individualities described above as originating through a geosynclinal make it desirable that they should have a distinctive name; and I therefore propose to call a mountain range of this kind a _synclinorium_, from _synclinal_ and the Greek ὄρος, mountain. This brings us to another important distinction in orographic geology—that of a second kind of monogenetic mountain. The _synclinoria_ were _made through a progressing geosynclinal_. Those of the second kind, here referred to, were _produced by a progressing geanticlinal_. They are simply the upward bendings in the oscillations of the earth’s crust—the geanticlinal waves, and hardly require a special name. Yet, if one is desired, the term _anticlinorium_, the correlate of _synclinorium_, would be appropriate. Many of them have disappeared in the course of the oscillations; and yet, some may have been for a time—perhaps millions of years—respectable mountains.