My vote would be for differnet species of Mts. That dark of an apperance isn't normal for the red ribbon mts that are also present in the picture. There even appears to be a texture to the shell. If I could see the opening I could make a better guess on whether or not it is a quilted melania.
I currently have 3 differnet species of MTS. Looking for more.
You can actually feel the dots. Trust me when I say no living snail looks like that in any of my tanks, only two have come up looking like that after they died.