Shell from Vietnam, Harp shell. (Harpa Major)

Harpa major, common name large harp, or major harp, is a species of large predatory sea snail, a marine gastropod mollusks in the family Harpidae, the harp snails and their allies.The size of the shell varies between 60 mm and 130 mm . The average adult reaches 3 1/2 inches and the shells have an ovate body with a heavily calloused spire. The columella, or the lower portion of the inside coil, has dark brown coloring. This marine species occurs off East Africa, Tanzania, Mozambique, the Mascarene Basin; off Hawaii

The shell (or snails also known as "snail") is one of limestone (calcite and / or aragonite) and other minerals existing (mostly) external skeleton, which is made by a mollusk (tribe of Mollusca). The shell gives the animal strength and protects the animal against external influences such as predation, injuries, dehydration, etc. The shell grows during the life of the mollusk. The science that studies all aspects of mollusks, called malacology. A branch of the malacology which only deals with the shell is called conchology. Previously it was considered wrong to state that malacology was not involved with the shell and the distinction between malacology and conchology was made by some very sharp. In current practice, the terms are often interchangeably, and they are more or less considered as synonyms. Shells can be used for the hardening of a passageway, which is then sometimes called a "shell path" is mentioned. Also, shells can be burned to lime shell, which is often used as a building material in the past, was used instead of cement.

 
Shells from Cebu.