Conchology (from Ancient Greek: κόγχος konkhos, "cockle") is the study of mollusc shells. Conchology is one aspect of malacology, the study of molluscs; however, malacology is the study of molluscs as whole organisms, whereas conchology is confined to the study of their shells. It includes the study of land and freshwater mollusc shells as well as seashells and extends to the study of a gastropod's operculum.
Conchology is now sometimes seen as an archaic study, because relying on only one aspect of an organism's morphology can be misleading. However, a shell often gives at least some insight into molluscan taxonomy, and historically the shell was often the only part of exotic species that was available for study. Even in current museum collections it is common for the dry material (shells) to greatly exceed the amount of material that is preserved whole in alcohol.
Conchologists mainly deal with four molluscan orders: the gastropods (snails), bivalves (clams), Polyplacophora (chitons) and Scaphopoda (tusk shells). Cephalopods only have small internal shells, with the exception of the Nautiloidea. Some groups, such as the sea slug nudibranchs, have lost their shells altogether, while in others it has been replaced by a protein support structure.
Versus shell collecting
The terms shell collector and conchologist can be regarded as two distinct categories. Not all shell collectors are conchologists; some are primarily concerned with the aesthetic value of shells instead of their scientific study. It is also true that not all conchologists are shell collectors; this type of research only requires access to private or institutional shell collections. There is some debate in the conchological community, with some people regarding all shell collectors (regardless of motivation) as conchologists.
Molluscs have probably been used by primates as a food source long before humans evolved. The Asturian culture of the European Mesolithic, in modern north Spain, is one of many coastal archaeological cultures around the world characterized by the creation of very large shell-middens or waste-heaps. The extremely large Whaleback Shell Midden appears to have been created over a period of 1,000 years or more.
Shell collecting, the precursor of conchology, probably goes back as far as there have been humans living near beaches. Stone Age seashell necklaces have been found, sometimes in areas far from the ocean, indicating that they were traded. Shell jewellery is found at almost all archaeological sites, including at ancient Aztec ruins, digs in ancient China, and the Indus Valley.
During the Renaissance people began taking interest in natural objects of beauty to put in cabinets of curiosities. Because of their attractiveness, variety, durability and ubiquity, shells became a large part of these collections. Towards the end of the 17th century, people began looking at shells with scientific interest. Martin Lister in 1685–1692 published Historia Conchyliorum, which was the first comprehensive conchological text, having over 1000 engraved plates.
George Rumpf, or Rumphius (1627–1702) published the first mollusc taxonomy. He suggested "single shelled ones" (Polyplacophora, limpets, and abalone), "snails or whelks" (Gastropoda), and "two-shelled ones" (Bivalvia). Many of Rumpf's terms were adopted by Carl Linnaeus. Rumpf continued to do important scientific work after he went blind, working by touch.
The study of zoology, including conchology, was revolutionized by Swedish naturalist Carl Linnaeus and his system of binomial nomenclature. 683 of the 4000 or so animal species he described are now considered to be molluscs, although Linnaeus placed them in several phyla at the time. The English word "conchology" was coined in the 1770s by the British Sephardi naturalist Emanuel Mendez da Costa, who published The Elements of Conchology: or, an Introduction to the Knowledge of Shells  in London in 1776.
There have been many prominent conchologists in the past two centuries. The Sowerby family were famous collectors, dealers, and illustrators. John Mawe (1764–1829) produced arguably the first conchology guidebook, The Voyager's Companion or Shell-Collector's Pilot as well as The Linnæan System of Conchology. Hugh Cuming (1791–1865) is famous for his huge collection and numerous discoveries of new species. Thomas Say wrote the fundamental work American Conchology, or Descriptions of the Shells of North America, Illustrated From Coloured Figures From Original Drawings, Executed from Nature in six volumes (1830–1834).
R. Tucker Abbott was the most prominent conchologist of the 20th century. He authored dozens of books and was museum director of the Bailey-Matthews Shell Museum, bringing the world of seashells to the public. His most prominent works are American Seashells, Seashells of the World, and The Kingdom of the Seashell.
Many of the finest collections of seashells are private. John DuPont and Jack Lightbourne are known for their extensive collections. John DuPont donated his shell collection to the Delaware Museum of Natural History in 1984. Emperor Hirohito of Japan also amassed a huge collection, and was a competent and respected amateur conchologist.
Many museums worldwide contain very large and scientifically important mollusc collections. However, in most cases these are research collections, behind the scenes of the museum, and thus not readily accessible to the general public in the same way that exhibits are.
The largest assemblage of mollusc shells is housed at the Smithsonian Institution which has millions of lots representing perhaps 50,000 species, versus about 35,000 species for the largest private collections.
- Academy of Natural Sciences, Philadelphia
- American Museum of Natural History, New York City
- Bailey-Matthews Shell Museum in Sanibel Island, Florida: the only museum in the world dedicated entirely to shells.
- Charleston Marine Life Center, Oregon Institute of Marine Biology in Charleston Oregon
- Denver Museum of Nature & Science, Denver, Colorado: approximately 17,500 shell lots.
- Museum of Comparative Zoology at Harvard, Massachusetts
- National Museum of Natural History, Washington D.C. – The Smithsonian Museum of Natural History has one of, if not the, finest shell collection in the world
- Austria, Vienna – Naturhistorisches Museum
- Belgium, Brussels – Royal Belgian Institute of Natural Sciences, one of the three largest collections
- France, Paris – Muséum national d'histoire naturelle
- Germany, Berlin – Berlin's Natural History Museum
- Netherlands, Leiden – Natural History Museum, Leiden
- Sweden, Stockholm – Swedish Museum of Natural History
- United Kingdom London – Natural History Museum Manchester – the Manchester Museum has the fourth largest mollusc collection in Britain with 166,000 lots.
Like other scientific fields, conchologists have a number of local, national, and international organizations. There are also many organizations specializing in specific subareas.
- Association Française de Conchyliologie
- Belgian Society for Conchology
- Club Conchylia, the German/Austrian Society for Shell Collecting
- Conchological Society of Great Britain and Ireland
- Conchologists of America
- Conquiliologistas do Brasil
- Nederlandse Malacologische Vereniging
- Unitas Malacologica
Shell collectors who purchase shells from dealers may sometimes encounter shells which have been altered to represent new species or rare color varieties. It is claimed that in previous centuries, fake examples of Epitonium scalare were created out of rice paste.
Depictions of shells on stamps and coins
Shells have been featured on over 5,000 postage stamps worldwide.