This name is said to have priority . The other names are junior synonyms . Exceptions to the rule of priority are made when a junior synonym is so widely used that it would threaten the stability of nomenclature to resurrect an unused senior name, and in cases of homonymy. Homonyms are identical names. For genus-group names to be homonyms, they must be identical, letter for letter.
Primary homonyms are identical species-group names first introduced in the same genus.
A junior primary homonym is permanently invalid, so Cernohorsky replaced Mitra gracilis Reeve with Cancilla gloriola Cernohorsky, 1970. Secondary homonyms were named in different genera, but later came to be classified in the same genus. Cypraea mantellum is the valid name for the species if it is placed in the genus Cypraea . The name Cypraea mariae must not be used. The concepts of valid and available are often confused.