Shell from Vietnam, Murex shell. (Chicoreus Kawamurai)

Bolinus brandaris (originally called Murex brandaris by Linnaeus and also Haustellum brandaris), and commonly known as the purple dye murex or the spiny dye-murex, is a species of medium-sized predatory sea snail, an edible marine gastropod mollusk in the family Muricidae, the murex snails or the rock snails.This species is known in the fossil record from the Pliocene (age range: from 3.6 to 2.588 million years ago). Fossil shells of this species have been found in Cyprus, Spain and Italy

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.