教えて下さい

“Undrrstanding English Grammar”という本に引用されている文で

6. Then the boy was moving, his bunched shirt and the hard, bony hand between his shoulder-blades, toes just touching the floor,
across the room and into the order one, past the sisters sitting with spread heavy thighs in the two chairs over the cold hearth,
and to where his mother and aunt sat side by side on the bed, the aunt’s arms about his mothers shoulders.[William Faulkner]

という文の意味が分かりません。
この“his bunched shirt and the hard”とは一体何を言っているんでしょうか？