the crewman who stood blocking their escape wore what would have been a neat , crisp white uniform on a man with the right proportions , but as he lacked the square shoulders and the long arms and legs , as he , in fact , had a shape best described as a potato with twig limbs , and a grey , sardonic face with sagging jowls and a salt and pepper hair cut that looked rather like the spines of an aged and balding porcupine .