Both Tridacna gigas, one of the world's largest shells, and Pisidum, the world's tiniest shell, can be found under Philippine waters. Tridacna gigas grows as large as one meter in length and weighs 600 pounds while Pisidum is less than 1 millimeter long. A shell called glory of the sea (Connus gloriamaris) is also found in the Philippines and considered as one of the most expensive shells in the world.


Source: http://home.planet.nl/~fortgent/Traveling/Philippines/Zamboanga.htm