Here are two pictures of a shell I found in 2007 while snorkeling in Roatan.  (The pictures are fairly large - sorry about that.)  I am just curious what it is since it is very pretty and I have have never seen one with both halves attached and no holes in the shell itself.  My wife has it in our curio cabinet because it is that nice. I am total novice at this, so any help would be greatly appreciated.  You can just email directly at tpage@msu.edu.  Thanks in advance. http://www.msu.edu/user/tpage/shell2.html

Dont worry about your mistake. It is very common to do it. I think your bivalve could be a Tellina, but I dont know the specie level.
Regards,
Rafa

This is Tellina radiata Linne., common name "sunrise tellin", a common Caribbean species.

Thanks.  Is it common for the shell to have both halves still together like that?  

In bivalve molluscs the two valves (the two halves of the shell) are usually held together by a fibrous band called the hinge ligament, located at or near the hinge. Once the animal dies and the muscles and other soft tissues decompose, the ligament is the only thing holding the two valves together. In some bivalve families the ligament is quite large and tough, and therefore it is common to find paired shells on the beach. In other families the ligament is rather thin and fragile, and easily broken when the shell is tossed around in the surf, so matched pairs are quite uncommon on the beach. In tellins the ligament is moderately thin, so matched pairs are usually not too common on the beach, though it is not unusual to find a few. When large numbers of paired bivalves are on the beach it is usually an indication that they were thrown up onto the beach alive by heavy surf during a storm, died there from the heat of the sun, and the soft parts were then eaten by birds, crabs, etc.

Thanks for information.  It is very helpful.   I actually found it about 20 yards off the beach in about 6 feet of water.   We will keep it in our curio cabinet as a souvenir of the trip.