Backless Square-Neck Long Prom Dress: Atria 6712HRaise the style bar in this open back long prom dress 6712H by Aria Couture. With a ruched square neckline, this curve hugging long dance dress has thin shoulder straps that criss cross the open back for an alluring look at prom, galas, and other black tie events. In misses and some plus sizes, this beautiful long formal dress has a hip hugging long mermaid skirt that opens in a side slit before draping into a small train that completes the design.