A recently discovered sheltered rock scar covered with red pictographs, in Jalisco, west Mexico, is a major addition to the rather meager data on pictographs in Mesoamerica. It appears to contain a complex set of data pertaining to the cosmology of the relatively unknown Indians who inhabited the Jalisco coast during the last Pre-Hispanic period. Analysis of the scar has incorporated both the artistic symbolism of the nearby Huichol Indians, and concepts developed through archaeoastronomy. This analysis suggests that the ceiling pictographs record the use of sky transits of the sun, Venus, or the constellation Orion as wet-season/dry-season calendrical markers. Wall pictographs show the sun on the mountainous horizon, below which is the earth filled with symbols of plants and animals; among these stand shamans calling down the life-giving rain from the god(s) of the sky. I also explore the possibility that one of the ceiling pictographs is a record of the appearance of the Crab supernova in the sky in A.D. 1054.