The fact that the serpent was a prominent object with them as with the Nahuatl tribes tends to link the tribes who made these symbols with the Nahuatl tribes. The serpent symbol, especially the feathered kind,[58] belongs mainly to the tribes of the Mexican region, where the rattlesnake exists in its greatest variety. The rattlesnake was highly venerated, and tribes as far north as the Moki country in the West, and perhaps as the Ohio in the East, might be correctly called the Snake people. There is nothing improbable in supposing that some of the tribes of the Mississippi valley, if they were not of the same stock as the Aztecs, were in tolerably close communication with them, or with tribes intermediate between the two. [Illustration: SHELL GORGET, TENNESSEE] Sometimes there occur markings on the rocks in the South-west that would be a puzzle to us did we not know, through the Mokis, who are still making them, just what they are. There is therefore no room for the imagination; the long scratchings are only grooves made in sandstone by the Moki farmer sharpening his planting stick. [Illustration: CUP MARKINGS] Another kind of rock markings, the so-called cupped-stones or cup markings, about which there has been a vast amount of discussion, may be considered here because they have generally been thought to have symbolic significance. That some of them may have had such significance is admitted below, but the bulk of those on this continent it seems possible to explain without resort to symbolism. An explanation which I offer, for what it may be worth, I have never seen suggested, though the idea may not be new. It is well known that the common form of fire-drill in use from one end of this continent to the other was that in which the end of a straight stick is made to rotate back and forth in a rounded cavity in another stick of softer wood called the hearth. In order that the operation should be speedily successful in producing fire, it was necessary to have the end of the drill convex, so that it would immediately bear as nearly as possible on the whole surface of the hearth cavity. In order to produce this convexity, the Amerind pecked a small cavity on a slab or rock of sandstone, and when he had it in the proper condition, he could bring his drill very quickly to the desired convexity, and also give it a roughness of surface that would contribute to the friction. As the fire-drill was long in constant use, many cavities were necessary, for a cavity would grow too deep, or for some other cause would not be adequate. A new hole would then be made, and thus in the course of time there would be numbers of the cavities on a rock or slab, which was convenient or had been found to possess the right texture for the purpose. My opinion, therefore, is that these so-called “cup markings” or “cupped” stones were in America the result of the sharpening of fire-drills, just as the long