From the Ananga Ranga. Lying on her back the woman bends her legs at the knees and draws them back as far as she can. Her partner enters from the kneeling position. Not great if your not flexible and can get tiring but the depth of penetration is worth it!
Very similar to the press positions in our him on top positions section this position allow him greater access and penetration.
One word, deep.
You can also get your partner to hold your legs down or you can wrap them around him, just be careful with the thrusting!