Who is Black Dog from Treasure Island and what is their importance?

Black Dog, whose distinguishing mark is two missing fingers on his left hand, is the first pirate to find Billy Bones. Black Dog fights with Bones and is injured but manages to run away. He is later seen with the blind man Pew who wants to find the treasure map. Later in the story, when Jim Hawkins first meets Long John Silver, Black Dog is sitting in the pub. When Hawkins points him out, Silver denies knowing him. This is Stevenson's first hint that Long John Silver might not be as honest as he pretends.