Okay. Couldn't resist. Had to look it up
They're pantyhose. Here's two more shots from the details section of Style.com. One is another angle of this shoe where you can see the footie part of the hose in the back, too & the other is of the hose worn with another shoe. I believe the black part is for the black line down the back of the calf. The satin shoe is actually a slingback, too, but I couldn't tell before because of the footing on the hose. Rather tacky with slingbacks and open toes I think. But based on that, I go back to a Yay on the shoe itself (just without footed hose)!

