In most species of tortoise, females will have significantly smaller tails than male tortoises do. If your tortoise has a long tail, he is most likely a boy. If your tortoise has a short, or even nubby-looking tail, then she's probably a girl. It’s really hard to tell what the tail looks like from the picture you posted. I’m not as familiar with identifying sex by the shell notch but I think that males have a V-shaped notch and females have a more U-shaped notch