The only valid name is Perotrochus hirasei. Pleurotomaria hirasei is often
used by dealers and book writers but this is incorrect. The genus
Pleurotomaria has only fossil species and no recent ones.
Went to watch your site. This is also a hirasei.
Some more about the genera: the genus Mikadotrochus is a synonym of
Perotrochus. There are only two recent genera: Perotrochus, with a short and
wide slit, and Entemnotrochus with a very long but narrow slit. Most of the
Pleurotomariidae belong to Perotrochus. Only two species and one subspecies
belong to Entemnotrochus (rumphii, adansonianus and adansonianus
bermudensis).

Best regards,

Kevin