Lower ab exercises

What's a good exercise for a female's lower abs? I do sit ups and crunches, but nothing seems to define my abs on the bottom. Any suggestions?

http://www.theabsdiet.com
You have to include diet.

I'm a thin girl, so I dont need an entire diet plan, just a few suggestions for some exercises to define my lower abs. Thanks for the ones already given, but does anyone else have any other suggestions?

it's very hard to work the lower part of your abs as i've been doing it the past 2 months in gym but the best excercises are mainly cardio....jogging, rowing , cycling it burns complete body fat and i've already lost a size in my jeans from 32 to 30....if you want I could get you a program for your lower abs...

ya i do this ..lay flat on ur back. raise ur feet and ur stomache at the same time..but dont raise ur lower back, try to keep it tuchin the floor.
it may be to defecult so u can use ur arms by rasing them to...but just a little help wont hurt.
do this 20 times , 3 sets.
if u do this every day for a week am sure ull get ur six packs

You cant train your lower abs. There's no such thing. The abdominus rectus is one muscle that spans the distance between the ribs and pelvis. Due to the all-or-nothing reaction of muscular energetics, it is biologically impossible to train one part of a muscle more than any other part of that same muscle. The reason you cant see your lower abs as much as you can your upper abs is there's usually a layer of fat covering the lower ab area.

How do you get rid of that? 20 minutes of cardio followed by 30 minutes of brisk walking is the most effective way to reduce body fat. Spot reduction is impossible, and where your body takes fat away from first is genetically predetermined. Just keep trying to lose fat until you finally see your lower abs.

As far as ab exercises go, squats and deadlifts are really the best.

There is also liposuction or Phosphatidylcholine shots called fat reducing injection(non fda approved). They are not exercise, but do show promising results at a high risk.

it's correct to say you can't spot reduce fat so as an abdominal nut I'll give you advice do cardio for about 20minutes a day do your crunches for abs and obliques then do leg lifts where you lie flat on your back legs straight and raise them from a 20 degree angle to about an 80 degree angle. another one is reverse crunches lie on you back chins 90 degrees parallel to the floor then just lift your pelvis and knees toward your head. do it in a controlled way though then lie with feet flat on the ground and just squeeze your pelvis up and contract it. those are a few to get you started then there are ways to add weight and a more advanced thing such as the captains chair if you have access to a gym.