Purpura (gastropod)

Purpura is a genus of marine snails, specifically gastropod mollusks, belonging to the subfamily Rapaninae within the family Muricidae—commonly known as murex or rock snails. This genus should not be confused with the name Purpura Jousseaume, 1880, which is actually a synonym for Bolinus Pusch, 1837. Members of Purpura have large shells with wide openings, a concave columella, and no outer calcitic layer; their rachidian teeth feature prominent marginal denticles.

The shell itself is oblong-oval with a large body whorl and a short spire. The aperture is ovate and large, with an oblique groove or channel at the front. The columella is flattened, and the outer lip is simple. These snails and their close relatives live in both temperate and tropical seas.

Many species produce a fluid that yields a dull crimson dye, which is why they are called purple shells. Their egg-cases are membranous, oval or spheroidal, sometimes found singly and sometimes grouped in masses; each sac contains many embryos. Recognized species include Purpura bufo, Purpura panama, Purpura persica, and the extinct Purpura angsanana and Purpura dijki. Over time, hundreds of species were once placed in this genus but have since been reassigned.

For example, Purpura hippocastanum is now Thais (Thalessa) virgata, Purpura hystrix is Drupa (Drupa) ricinus, Purpura lapillus is Nucella lapillus, Purpura mancinella is Thais (Mancinella) alouina, Purpura nassoidea and Purpura nassoides are both Oppomorus noduliferus, and Purpura rudolphi is a synonym of Purpura persica.