Furrer's black outlines (and occasional black skies), long limp snakes and generally loose lines have an Ungerish look, but his cartoon tortoises--goofy at play and most pitiful in shame--have primordial schleppiness all their own. The story unfolds quite naturally from a familiar indiscretion to an absurb cover-up: When a strange turtle visits their island the tortoises are so jealous of his swimming that they rashly boast of being able to fly; then they are reduced to dyeing the seagull friends with blueberries so that, thus camouflaged, the gulls can carry them across the sky. Their ploy doesn't work but it all ends happily anyway in a moonlight dance . . . and good fun all round.