Turtle Turning Wearing its storm-trooper’s helmet  which is both rain-shelter and armour against predators  my nephew’s pet turtle moves across its table-sized enclosure, crushing  down the grass the way a Russian tank rolls over the debris  scattered through a ruined city;   its long-necked narrow head might  belong to a snake, though it revolves in reconnaissance  just as a periscope extends, especially when the reptile  submerges in the pool at the centre of its domain  to become a submarine.   The pattern on the turtle’s shell  is like a map of the world, or of the earth’s tectonic plates,  but…