Here's a long black strapless prom dress that is as sparkly as it is seductive. With a sheer corset-style bodice, this gorgeous long black designer dress shimmers with sweeping sequin designs from the sweetheart neckline to the floor. The strapless sequin formal dress includes a fully-lined long skirt with a sequin sheer overlay that opens in a side slit for a flirty look at prom, black-tie formals, and other very special occasions. Sold exclusively at PromGirl, this elegant long black…