"Superimposed over the cribbing are curious motifs that resemble masks or perhaps shields. They are unique to this building. A central mosaic face or mask with deep eye and mouth holes surmounts a scaled or mosaic base. Over the face is a headdress-like device consisting of concentric bands of shells and jewels, cropped feathers, and twisted cords or feathers.
Elements resembling spearthrower darts protrude from the upper corners. An odd device decorated with knots covers the nose and a "tongue" emerges from the mouth hole. If the corner devices are indeed spearthrower darts, then the central image may represent a shield, possibly as a symbol of warthe arrowshieldknown to have been used by the Maya and other Mesoamerican peoples."
Linda Schele & Peter Mathews, The Code of Kings, p. 268-9.