difference between cypraea zebra and cervinetta

[shellhunk]

I just grouped my carneolas from the leviathans. The carneolas are from 72-75mm. Big sizes but no bumps on the margins. The leviathans from 74-80mm they all have those bumps on the margin with callousing.
One mystery to me - one, size 62mm, is calloused and with typical bumps on the margin. Good gloss and aside from a thin growth line, no dorsal problems. Not a carneola, right? Because of the marginal nodules.  <img src="images/smiley/confused.gif" alt="" border="0" />

Chris