black on bottom of shell and white in the creases on the top shell!! HELP!

by rachel
(michigan)

i was in florida and i noticed that a gopher tortoise had black o nthe bottom of his shell and also...inbetween the shells creases on top of his shell...there was a white outline...sooo i wondered what that those things were... i REALLY want to know because ever since i have been worried about that tortoise!