The Nahua day sign, _Cozcaquauhtli_, as previously noted, has the meaning vulture, and we naturally find this bird frequently represented in the Mexican codices. In the Nuttall Codex, the head of the king vulture occurs repeatedly as a glyph for this day. In its less modified forms (Pl. 18, figs. 2-4), the beak is merely a pair of flattened rami, surmounted proximally by the conspicuous quadrangular knob. The minute hair-like feathers on the otherwise naked head are shown as a fringe at the throat and crown, while a conventionalized ear is represented posteriorly. A series of interesting figures (Pl. 18, figs. 5-10) illustrates steps in the further reduction of this head to a small glyph in which only the beak with its large squarish knob remains (Pl. 18, fig. 10). BLACK VULTURE (_Catharista urubu_). It is difficult to assign any single characteristic to the figures representing the black vulture (Maya, _t[vs.]om_) other than the long raptorial beak. A number of drawings probably depict black vultures, though this cannot be certainly affirmed. Such are those shown in Pl. 18, figs. 11, 12, 14, 17; Pl. 19, figs. 2-4, 13, 14. Stempell considers the vulture shown in Pl. 18, fig. 13, to be a king vulture, but it has no knob on the beak, and thus is quite likely the black vulture. The fact that its head is shaped much like that of the god with the king vulture head (Pl. 17, fig. 3) would indicate merely the individuality of the artist. The coloring of the species under discussion is uniformly black in the Dresden and Tro-Cortesianus, except in certain cases where the birds are shown in outline only, as in Pl. 19, fig. 12. It is not certain, however, that these two last are black vultures, though they suggest the species. The two birds shown in Pl. 19, figs. 5, 6, are almost surely black vultures, and, as represented in the manuscript, are descending upon a man. Stempell thinks they may be ravens, but this is very doubtful, for the raven probably was unknown to the Mayas, since its range is to the northward. What appears to be a crest is seen on the head of the bird in Pl. 19, fig. 4. The black coloring and the shape of the bill otherwise suggest the black vulture, though perhaps the crest would indicate the harpy eagle. Similarly, Pl. 19, fig. 14, is provided with a sort of tuft or crest, but its general appearance is suggestive of the vulture. A pottery whistle (text fig. 2) from the Uloa Valley evidently represents a black vulture. The head of the bird shows the characteristic wrinkled appearance seen in the drawings, with the heavy beak. The absence of the rostral knob would preclude its being a king vulture. [Illustration: FIG. 2. POTTERY WHISTLE, VULTURE. ULOA VALLEY, HONDURAS.]