Jaguar mask graces Xpujil's Río Bec towers
The well-preserved uppermost stucco mask on Structure I's central Río Bec style tower. The plate on the right shows how this mask appeared during the Carnegie Expedition in 1938.
(Ruppert 1943:Plate 40b)
Paul Gendrop mentions a different aspect of these buildings: "Another feature which I think interesting to mention is the existence of those strange "sight tubes" or "observation ducts" that frequently go throught the mass of a simulated temple or a large tower, as in the case of Rio Bec B, Xpuhil, the side abutment of Structure V at Hormiguero, or that strange cylindrical tower at Puerto Rico. Usually horizontal and rectilineal (except for a few deliberate offshoots in the Puerto Rico tower), they might have functioned as part of some signaling system or light communication, perhaps from one city to another, as could have been the case with the ducts that transpass the whole base of the rear pseudo-temple at Xpuhil and might have been seen from the narrow window on the third level of Structure IV at Becán, situated almost seven kilometers away on an evident east-west axis."
Gendrop: 1989, p 62