Michael,

What Angie says here is helpful and accurate. Particularly, use the panel title (the folded title as seen when it comes out of the magazine) as the 245 title if it "collectively" represents both maps involved. Otherwise, Linda's suggestion is appropriate EXCEPT one does not put the second title after a $b in the 245 because that subfield is for "other title information" -- meaning additional title text from the primary title (usually text that is in smaller font or located farther away from the chosen title proper). Instead, separate the two different titles by a semi-colon and then as Angie points out be sure to put that second title in a 246 field.

In these cases where you are trying to make sure that both maps are "equal" in prominence what I have learned to do in recent years is make sure to be consistent throughout the record in terms of indicating that there are TWO "main maps" rather than one being more prominent than the other. That means two titles in the 245 (with the second one going into a 246 so it too is discoverable), two scale statements (and therefore 2 034 coded fields if applicable, on rare occasions the two maps have been done at the same scale and for the same geographic area (coordinates)), a physical description such as what Angie has laid out, subject headings that apply to topics on either/both map(s), right down to making sure that when I formulate "Includes" notes that they are specific to each map, usually in the form of something like "Regional map includes..." and then "World map includes..."

I think if you look over any of the records I have done in the past 5 years or so (see OCLC symbol UPM in the 040 field) you will see a methodology that reflects what you are after. 

Paige Andrew

Cartographic Resources Cataloging Librarian

Penn State University