From http://www.christinehaynes.com/:
"The Derby Dress is a fun swingy a-line sundress. Both versions pull on, feature princess seams in the front, and have four panels in the back.
View A has a contrast Peter Pan collar, straps at the neck, and a gathered ruffle at the hem that hits above the knee.
View B has a bias-cut gathered ruffle at the neck, a tie belt at the waist, and hits just above the knee."