A girdle is part of the

anatomy Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...

of a

chiton Chitons () are marine molluscs of varying size in the class Polyplacophora (), formerly known as Amphineura. About 940 extant and 430 fossil species are recognized. They are also sometimes known as gumboots or sea cradles or coat-of-mail s ...

, one class of marine

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

s, the class Polyplacophora. The shell of a chiton consists of eight

valves A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings ...

which articulate with one another. The girdle is a strong but flexible structure that in most cases encircles the plates, holding them all together. Details of the external surface of the girdle are often useful in identifying the

taxonomic Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

family, genus and species of chiton. For example, the girdle may be covered in overlapping scales, spikes, or it may have tufts of glassy bristles protruding from it. In a few genera of chitons, the girdle covers the valves either partially, as in the Black Katy chiton, or completely, as with the gumboot chiton.

References

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Glossary entry for molluscan terminology

Some general info on chitons
Mollusc anatomy