Nor is this feature of Maya writing (i. e., the presence of "head variants") the only pitfall which awaits the beginner who attempts to classify the glyphs according to their appearance. In some cases two entirely dissimilar forms express exactly the same idea. For example, no two glyphs could differ more in appearance than _a_ and _b_, figure 12, yet both of these forms have the same meaning. This is true also of the two glyphs _c_ and _d_, and _e_ and _f_. The occurrence of forms so absolutely unlike in appearance, yet identical in meaning, greatly complicates the problem of glyph identification. Indeed, identity in both meaning and use must be clearly established before we can recognize as variants of the same glyph, forms so dissimilar as the examples above given. Hence, because their meanings are unknown we are unable to identify _g_ and _h_, figure 12, as synonyms, notwithstanding the fact that their use seems to be identical, _h_ occurring in two or three texts under exactly the same conditions as does _g_ in all the others. [Illustration: FIG. 12. Normal-form and head-variant glyphs, showing absence of common essential element.] A further source of error in glyph identification is the failure to recognize variations due merely to individual peculiarities of style, which are consequently unessential. Just as handwriting differs in each individual, so the delineation of glyphs differed among the ancient Maya, though doubtless to a lesser extent. In extreme cases, however, the differences are so great that identification of variants as forms of one and the same glyph is difficult if indeed not impossible. Here also are to be included variations due to differences in the materials upon which the glyphs are delineated, as well as those arising from careless drawing and actual mistakes. The foregoing difficulties, as well as others which await the student who would classify the Maya glyphs according to form and appearance, have led the author to discard this method of classification as unsuited to the purposes of an elementary work. Though a problem of first importance, the analysis of the simple elements is far too complex for presentation to the beginner, particularly since the {26} greatest diversity of opinion concerning them prevails among those who have studied the subject, scarcely any two agreeing at any one point; and finally because up to the present time success in reading Maya writing has not come through this channel. The classification followed herein is based on the general meaning of the glyphs, and therefore has the advantage of being at least self-explanatory. It divides the glyphs into two groups: (1) Astronomical, calendary, and numerical signs, that is, glyphs used in counting time; and (2) glyphs accompanying the preceding, which have an explanatory function of some sort, probably describing the nature of the occasions which the first group of glyphs designate.