PURPURA. 



Lam. {Buccinum undo sum. Linn.)', he has made Lamarck's 

 Genus Riciiiula contribute nearly if not quite all its spe- 

 cies, and Columbella several, to ornament this already too 

 extensive and overgrown family. Some of the alterations 

 thus made by Duclos we consider as improvements, others 

 we cannot praise. The union of Concholepas, Avhose shell 

 may always so easily be distinguished from all the Purpu- 

 rse, we cannot approve. Triton undosus of Lam. though 

 certainly ill assorted when placed with Triton, does not 

 appear to us to be more naturally associated with Purpura ; 

 it approaches nearer to Columbella, and we suggest the 

 probability of its forming a well distinguished Genus in 

 union with several other cognate species*. We see no 

 objection to the union of the Lamarckian Ricinulae and 

 some of his Columbellae with Purpura, because we find a 

 number of species which it would be difficult to refer to 

 the one Genus or the o!her when regarded as distinct, but 

 which are naturally associated when united under 

 Purpura. 



Purpura is a Genus of marine shells, which in common 

 with several other pectinibranchous Gasteropoda produces 

 a purple secretion, which under some circumstances has 

 formerly been used for dying, and might perhaps still be 

 employed advantageously for that purpose. The species 

 are very numerous and belong to all temperate and tropical 

 climates. Some are found on our own coasts. The ova 

 are deposited in small coriaceous vessels of various shapes 

 according to the species, each having a stem, by the base 

 of which they are affixed to shells, stones and other 

 submarine substances. 



The Purpuree are for the most part ovate or oblong 

 shells, generally with a short spire, and most frequently 

 grooved, granose or tubercular or spinose externally; 

 their aperture is generally large, somewhat spreading and 

 ovate, its outer lip is often crenated, and it is sharp-edged, 

 also commonly toothed near the margin within : it is 

 notched and has a short canal at its anterior or basal 

 extremity : the columellar or inner lip is mostly flattened 



* Since the above was written Mr. Gray has separated the last mentioned 

 Shells from Purpura, under the generic appellation of Pollia. 



