Although the Ozark region has not yet received sufficient attention to dull its charm for the explorer, the fact has been established that its earliest sedimentary rocks are of the Cambrian Age and still occupy mainly the position in which they were originally deposited. Therefore we need not be surprised to discover that some, at least, of the excavations are proportionately ancient; and that the Natural Bridges are the last remaining positive evidence of their former existence and final collapse. That the Natural Bridges of Missouri mark the destruction of more ancient caves than the one preserved to geological history by Virginia's grand attraction, seems quite evident. The greater age of the rocks indicates the possibility of earlier excavation while their undisturbed position suggests that destruction resulted, not from violent earth movement, but from the slow action of agencies requiring long periods of time. Before proceeding to a discussion of the caves visited personally for the gratification of private interest, it is desirable to know what attention has been given to the subject, incidentally, in the course of regular official duty on the Missouri Geological Survey. CAVES DESCRIBED IN THE STATE REPORTS. Although many unknown caves must yet be discovered in the imperfectly explored portions of the vast Ozark forests, these finds are already so numerous as to seldom attract attention according to their just desserts. One of the comparatively recent of these discoveries is Crystal Cave, at Joplin, described on page 566, Vol. VII., Missouri Geological Survey Report 1894.[1] It was opened in the lower workings of a shaft of the Empire Zinc Company, and "The entire surface of the cave, top, sides and bottom, is lined with calcite crystals, so closely packed together as to form a continuous sheet and most of them of great size, and well formed faces. Scalenohedra as much as two feet long are sometimes seen, and others a foot or more in length are common. Planes or crystal ghosts, sometimes with pyrite crystals, marking stages of growth in the calcite crystals, are often distinguishable. The entire absence of anything like stalactites is noticeable, and together with the presence of the crystals, show that the cave was completely filled with water during their growth." In the same volume, all those counties in the extreme southwest corner of the state, whose geological age has not heretofore been considered positively determined, are mapped as Lower Carboniferous, and Lower Silurian, with the Coal Measures covering portions of Barton and Jasper and appearing in a few small, scattered spots in Dade, Polk, Green and Christian counties, and some scanty lines of Devonian fringing the edges of the Silurian in Barton and McDonald.