Hi Linda,
     I'll see what I can figure out; I'm an amateur's amateur. But I can
     recommend trying the book Sea Shells of Tropical West America by Myra
     Keen (Stanford University Press, c. 1971). I've been using it to id
     shells I found in Puerto Vallarta in March; it's helpful because it
     has stuff not in the Compendium everybody talks about. If your local
     library doesn't have it, maybe they can borrow a copy through their
     Interlibrary Loan Dept. Hope this helps!
 
     Sue in Denver