Hello Jennifer, Any book wide enough in scope to be arranged by geographic zones would necessarily not be very comprehensive, and such "overview" types of books are most useful when arranged by taxonomic relationships (by families). The Compendium of Seashells is perhaps the best known example of such a book. This book is worldwide in scope, and therefore necessarily covers only a fraction of the species in any one family of shells, or in any one geographic area. Therefore it would be very cumbersome to identify, for example, a cone shell of unknown origin if you had to check the Panamic section, the Australian section, the Mediterranean section, the Caribbean section, etc. No single work could even attempt to cover all the species in all the geographic zones. Moving beyond this general type of book, you find two principle groups of comprehensive identification guides - those which deal with one family of shells worldwide, and those which deal with all families in one well defined geographic area. These books are usually the most useful ones for advanced collectors, because there is a high degree of probability that the shell you are trying to identify is actually in the book. In contrast, trying to identify an unknown Terebra or Cymatium (or worse, a bivalve) from the Compendium, you start out knowing there is only a 25% chance (or maybe a 5% chance in the case of a venus clam or a cockle) that the species you have is included in the book. THE book for the Panamic Province is Seashells of Tropical West America by Myra Keen. It is not the easiest book for a beginning collector to use. It is a large book (3 inches thick), with thousands of small, black and white pictures (mostly photographs but some line drawings). Still, there is simply nothing comparable if you are trying to identify an unknown shell picked up between Baja and Peru. This book is available from Amazon.com for $79.50. Regards, Paul Monfils