This is a small opaline tortise shell sitting inside a larger shell of the same color. The smaller one is no bigger than my rhumb nail, and the larger one not much bigger, and about the size as a 20cent piece.
This is the "Inverted" version of the "Origional Shell above.
Baby abalone shells we call it. I have some in my portfolio too, but NONE like this. Imagine you could have better control over the depth of field. That 60mm just does not give you that privilege unless you use a ring flash. Fantastic macro.