Hi Andy,
 
I'd like a good answer to that, too.  Pectens can be as confusing as anything,
and they are constantly getting tossed from one genus to another.  Are
Annachlamys, Belchlamys, Coralichlamys Scaeochlamys, and others, considered
full genera, or are they subgenera of Chlamys?  I even heard that someone
suggested Gloripallium pallium and G. speciosum were one in the same.  Seems
ludicrous to me, if it is true.
 
Travis