Genus of gastropods
Purpura is a genus of sea snails, marine gastropod mollusks in the subfamily Rapaninae of the family Muricidae, the murex snails or rock snails.
Not to be confused with "Purpura" , a synonym of "Bolinus" 
Description.
The genus "Purpura" is characterised by having large shells with large apertures, a concave columella and no external calcitic layer. The rachidian teeth have prominent marginal denticles.
The shell is oblong-oval, the body whorl large. The spire is short. The aperture is ovate, large, with an oblique channel or groove at the fore part. The columella is flattened. The outer lip is simple. 
Distribution.
The "Purpura" and related genera inhabit the seas both of temperate and tropical climates. Many species produce a fluid which gives a dull crimson dye, whence their name of purple shells. Their egg-cases are membranous, oval or spheroidal, sometimes solitary, sometimes united in masses, each sac containing many embryos.
Species.
Species within the genus "Purpura" include:
In the course of time, several hundred species were included in the genus "Purpura".
References.
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