The Japanese of old didn't need air conditioning: They fought the heat by sending chills down each other's spines instead. Stories of imps, goblins and half-human anomalies-or better yet, actual examples of them-were as much a part of the summer as fireworks and festivals. Unfortunately, festival houses of horrors are hard to find these days. You could instead head for ``Unidentified Mysterious Animals in Japan,'' now playing at the Kawasaki City Museum. Organized in-house, the show gathers together hundreds of items-from scrolls to dubious fossils-that either show or purport to be mysterious creatures spotted over the past two centuries in the Japanese archipelago. Among the menagerie are snakes with women's faces, remarkably Godzilla-like lizards, seven-tailed foxes and -posed in fetal position in glass cases-the mummies of kappa water imps and mermaids. But be warned: The museum assumes these creatures are all malarkey and insists the exhibition is an attempt to show the social background that gave birth to these mythical beings. Thankfully, it fails and viewers can appreciate the objects here for their own sake. There's a certain freedom when you're working with imaginary monsters. Artists depicting them aren't held to rules of style or accuracy because they're showing something no one-probably not even themselves-has laid eyes on in real life. What happens with this freedom can be seen in a depiction of a dark monster supposedly dredged up by workers from the bottom of the Inbanuma marsh in northern Chiba Prefecture in 1843. According to written accounts, the angry creature-about 5 meters long with a 3-meter-wide face like a monkey's-brought rainstorms and killed 13 people. An unknown artist's rendition of it looks remarkably like Casper the Friendly Ghost (albeit in black), smiling and displaying a row of serrated teeth. Yet the naive style in which that and other creatures are shown may not have been naive after all. The artwork may have been bad on purpose, to give the sense that the illustrations were finished quickly, based on the descriptions by breathless witnesses. In fact, depictions of monsters, if not exactly an art genre, were sort of a cottage industry in pre-modern Japan. Images of mysterious creatures were being knocked off constantly for local kawaraban community bulletin boards, scrolls and later entire bestiaries for sale to collectors. Mummified monster remains, meanwhile, turned up as regularly as Catholic saints' fingers. Dried-up mermaids, desiccated water imps and dragons were not uncommon attractions at temples and shrines, where the items were presented as unusual gifts from nature, sometimes with powers to heal. To judge from their similarities, though, they must have been made in bulk at the same workshop.