Dear avril and Ross,
This shell is a Perotrochus hirasei. It is much heavier than teramachii and
the spire is completely different. For a good reference take the book "The
living pleurotomariidae" by Anseeuw and Goto. This book covers all recent
species (27) described before 1996. Since then there are two new species
described: P. indicus and P. boucheti.
Best regards,
Kevin