Hi, I'm new to this group and to conchology. I have a burning question,
unanswered by lots of googling, related to a 11-cm specimen that I collected
while snorkelling last week in Puerto Rico. It looks like it could be Cassis
tuberosa.

The shell appears to have grown in stages. A distinct bi-lateral lip is
formed, creating a flattened surface at the aperture. Then the shell is
extended two-thirds around the spiral and another lip structure is formed,
against one side of the former lip. This appears to have happened at least
six times in the life of my specimen.

So my question is: How does the animal do this? What does the shell look
like between the lipped forms, and how does the animal live? Further
confounding my understanding is the existance of an upturned "tail" on the
end opposite the spiral face. That structure could not continue to grow in a
self-similar fashion. So is it simply encased in the subsequent growth
cycle, along with other protuberances?

The shell almost doubles in diameter with each cycle. So the amount of
material that must be added in each cycle must be at least equal to the mass
of shell that existed. Does that mean that there is a final determinate
state beyond which growth is not possible -- leading to my finding of this
empty shell?

Thanks in advance for satisfying my curiosity!

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