77 



Scalaria and lanthina, as well as in Murex and Purpura; hence the 

 term Purpura was adopted by Lamarck to distinguish the genus under 

 consideration, regardless of any property with which the animal might be 

 endowed of secreting a purple juice. The most striking feature in the 

 soft parts of Purpura is that of the head being a little flattened, and pro- 

 longed at each extremity into the tentacles, without any prominence in the 

 centre; approximating in this respect to Buccinum. The tentacles are 

 pedunculated to generally two thirds of their extent, and at the summit of 

 the pedunculated portion are the eyes. The operculum which the animal 

 carries on the hind extremity of its disk, is invariably horny, and fits 

 closely to the aperture of the shell. 



The shell of Purpura is mainly distinguished by an ovate dilated growth, 

 emarginated at the base, with a more or less flattened columella, the spire 

 being sometimes extremely short, sometimes a little acuminated. There are 

 three closely allied genera, Concholepas, Monoceros, and Bicinula, which 

 the French authors propose to fuse into the present ; I have not considered 

 it prudent, however, to follow this course, as they afford good typical dis- 

 tinctions, and their amalgamation under the head of Purpura would only 

 tend to confusion by involving a change of names.* 



The Purpura vary exceedingly in their detail of sculpture, but are some- 

 what constant in colour ; the well-known P. lapillus of Europe varies in 

 both respects to an almost inconceivable degree ; indeed, no one who has 

 not thorouglily examined a numerous series of specimens can form an 

 adequate idea of its Protean character. 



Species. 



* In the monographs of Purpura and Rlcinula just published in the 'Conchologia Iconica ', I 

 have added to the importance of the latter genus by the introduction of some small species inter- 

 mediate between Purpura and Columbella, the greater portion of which were not previously 

 described. 



