Here's a few things i got off a site...
Not sure how accurate these are
MALE
1. Long claws on the front paws.
2. A fat tail and it is longer than a female's tail.
3. A slight concaved curve on the bottom part of the shell.
4. You might notice more aggressive tendencies.
5. The cloaca (opening) is closer to the tip of the tail than the body.
Female
1. Shorter claws than a male's claws.
2. A shorter, thinner tail.
3. Flatter plastron (bottom of the shell).
4. females tend to be larger than males.
5. The cloaca (opening) on the tail is closer to the body than the tip of the tail.