I'm going to disagree with that.
Vitro's mibs with two colors in one vane are so common that it has been concluded they were intentional and thus perhaps not deserving of the name hybrid. I've heard that said anyway.
I'm not saying not to call the Vitros hybrids but how can an intentional "hybrid" rob the name from, say, a marble which is truly a blend of more than one type, such as a changeover between runs.
Maybe a marble such as mine in post #3 could more accurately be called "error". But as of this morning I'm standing by hybrid as a great name for them. Maybe I'm wrong but I don't remember anyone else ever saying that the name only applied to Vitros.
Elizabeth? Paula? Am I full of it? . . . uh, on this subject? rofl
Okay, we need more pix. LOL. Words bad. Marbles good.