>Skull and Bones is a pirate's flag.
>[A small crumb which may mean something to someone along the way ^^^]
skull and bones, pirate flag crossed femurs and a skull
I believe that this imagery originated from using ossuaries to entomb the dead; specifically in the ancient Israel before and during the time of Christ.
Human remains were removed of all there flesh so just bones remained. In order to get them into the smallest burial boxes possible (an ossuary), the two femurs were crossed and the skull was placed between them.