After reading through the SPS eye candy thread I noticed that SDGuy identified a piece as a prostrata, but I thought it was a mille. What's the real difference between the two. I looked at pictures online and there's so many that must be mislabeled that I can't seem to find the difference. Is it the growth pattern or the shape of the coralites? I have a few in my tank that I always thought were milles, but now I'm not so sure. Here's some pictures of the pieces in question...
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