a seashell, perhaps a scallop shell, or possibly coral (see Karttunen); reddish in color; see the Visual Lexicon of Aztec Hieroglyphs for two visuals of tapachtli:
https://aztecglyphs.wired-humanities.org/content/tamapachco-mdz12r
https://aztecglyphs.wired-humanities.org/content/tamapachtli-fcbk9f18r
Tapach nocallin = My house is of coral
tapachtli = Vogde's scallop, lion's paw scallop; in case it is helpful, here's an image of the Pacific lion's paw: https://www.mexican-shells.org/pacific-lions-paw-shell/
"The 800 vermillion seashells also appear in the Matrítula an aare glossed tapachtli. Tapachtli is a kind of seashell that 'resembles a crystal; it is also translucent; it is also transparent, smooth, slick, ever slick, rough; it is rough, perforated' (Sahagún 1950–1982 11:230). They were cut and made into bracelets and necklaces (ibid.), and the atzcalli (a synonym for tapachtli) was called a 'physician's bowl' and used by physicians for divination (ibid.,: 60). The Información of 1554 (Scholes and Adams 1957:114) calls these 'piedras encarnadas de que ellos hacían máscaras.' Clark (1938 1:74) identifies thse as Spondylus princeps and suggests that they were probably provided by the towns of Çihuatlan, Çacatulan, Nochcoc, and Coyucac (ibid.)."
tapachtli = almeja voladora, almeja mano de león
Coming from far away at the Atlantic or Pacific coasts, seashells were prized in the central highlands. Mexicolore has drawings of the tapachtli. The Metropolitan Museum of Art has a tabard and necklace apparently made of tapachtli.
