In the inscriptions an Initial Series is invariably preceded by the so-called "introducing glyph," the Maya name for which is unknown. {65} Several examples of this glyph are shown in figure 24. This sign is composed of four constant elements: 1. The trinal superfix. 2. The pair of comblike lateral appendages. 3. The tun sign (see fig. 29, _a_, _b_). 4. The trinal subfix. [Illustration: FIG. 24. Initial-series "introducing glyph."] In addition to these four constant elements there is one variable element which is always found between the pair of comblike lateral appendages. In figure 24, _a_, _b_, _e_, this is a grotesque head; in _c_, a natural head; and in _d_, one of the 20 day-signs, Ik. This element varies greatly throughout the inscriptions, and, judging from its central position in the "introducing glyph" (itself the most prominent character in every inscription in which it occurs), it must have had an exceedingly important meaning.[42] A variant of the comblike appendages is shown in figure 24, _c_, _e_, in which these elements are replaced by a pair of fishes. However, in such cases, all of which occur at Copan, the treatment of the fins and tail of the fish strongly suggests the elements they replace, and it is not improbable, therefore, that the comblike appendages of the "introducing glyph" are nothing more nor less than conventionalized fish fins or tails; in other words, that they are a kind of glyphic synecdoche in which a part (the fin) stands for the whole (the fish). That the original form of this element was the fish and not its conventionalized fin () seems to be indicated by several facts: (1) On Stela D at Copan, where only full-figure glyphs are presented,[43] the two comblike appendages of the "introducing glyph" appear unmistakably as two fishes. (2) In some of the earliest stelæ at Copan, as Stelæ 15 and P, while these elements are not fish forms, a head (fish?) appears with the conventionalized comb element in each case. The writer believes the interpretation of this phenomenon to be, that at the early epoch in which {66} Stelæ 15 and P were erected the conventionalization of the element in question had not been entirely accomplished, and that the head was added to indicate the form from which the element was derived. (3) If the fish was the original form of the comblike element in the "introducing glyph," it was also the original form of the same element in the katun glyph. (Compare the comb elements () in figures 27, _a_, _b_, _e_, and 24, _a_, _b_, _d_ with each other.) If this is true, a natural explanation for the use of the fish in the katun sign lies near at hand. As previously explained on page 28, the comblike element stands for the sound _ca_ (_c_ hard); while _kal_ in Maya means 20. Also the element () stands for the sound _tun_. Therefore _catun_ or _katun_ means 20 tuns. But the Maya word for "fish," _cay_ (_c_ hard) is also a close phonetic approximation of the sound _ca_ or _kal_.