protruding from the back part of the mouth are as constant as any of the other elements. The head of the full-figure variant in figure 28 presents the same lack of essential characteristics as the head variant, though in this form the small curling fang is also found. Again, the body attached to this head is that of a bird which has been identified as an eagle. {70} THE TUN GLYPH [Illustration: FIG. 29. Signs for the tun: _a-d_, Normal forms; _e-h_, head variants.] [Illustration: FIG. 30. Full-figure variant of tun sign.] The period of the 3d place or order was called by the Maya the _tun_, which means "stone," possibly because a stone was set up every 360 days or each tun or some multiple thereof. Compare so-called hotun or katun stones described on page 34. The normal sign for the tun in the inscriptions (see fig. 29, _a_, _b_) is identical with the form found in the codices (see fig. 29, _c_). The head variant, which bears a general resemblance to the head variant for the cycle and katun, has several forms. The one most readily recognized, because it has the normal sign for its superfix, is shown in figure 29, _d_, e. The determining characteristic of the head variant of the tun glyph, however, is the fleshless lower jaw (), as shown in figure 29 _f_, _g_, though even this is lacking in some few cases. The form shown in figure 29, _h_, is found at Palenque, where it seems to represent the tun period in several places. The head of the full-figure form (fig. 30) has the same fleshless lower jaw for its essential characteristic as the head-variant forms in figure 29. The body joined to this head is again that of a bird the identity of which has not yet been determined. THE UINAL GLYPH [Illustration: FIG. 31. Signs for the uinal: _a-c_, Normal forms; _d-f_, head variants.] [Illustration: FIG. 32. Full-figure variant of uinal sign on Zoömorph B, Quirigua.] [Illustration: FIG. 33. Full-figure variant of uinal sign on Stela D, Copan.]