334 



Gasteropoda.- 



-MOLLUSCA.- 



-Pkoboscidifeka. 



power of reti acting the float. In rough weather, 

 however, they are driven about by the agitated sea, 

 and their floats are then broken or detached ; but even 

 then the shells are found floating on the surface. In 

 this state they are frequently drifted to our own shores, 

 especially on the southern and western sides of the 

 island ; and in Swansea bay, we are told, the animals 

 have been found quite fresh. The favourite food of 

 the lauthinae appears to be the gelatinous Velella, 

 and M. Deshayes informs us that he has often witnessed 

 them feeding upon those animals, and apparently 

 making use of them at the same time as a raft to float 

 them on the surface. It has been said that in cou- 

 Bequence of feeding upon these blue-coloured Acalephre 

 the lanthinoi obtain their violet hue. It is certain that 

 they have the power of secreting a quantity of violet 

 fluid, and that when molested they exude it in consider- 

 able abundance. 



THE COMMON VIOLET SNAIL {lanthina communis), 

 according to tlie late Professor Forbes, secretes this 

 fluid rapidly, and the purple dye, he says, was so 

 strong, that some paper which he painted with it in 

 1837, retained its colour strongly in 1853. M. 

 Lesson tried to prove that this was the very shell 

 which Pliny described as the one from which the 

 Tyrian dye was obtained. It occurs frequently in the 

 Mediterranean ; but the colour of the fluid of this 

 mollusk is purple on its emission, and is remarkably 

 defective in permanency. The species of lanthina are 

 not numerous, but some of them are difl'used over a 

 great part of the world, the shells being thrown up on 

 the sea-coasts by gales of wind. At certain seasons 

 the beaches of St. Helena and the island of Ascen- 

 sion are entirely covered with them. Mr. A. Adams 

 found them cast up by thousands on the shores of the 

 Jleiaco-shimah islands, but he says he never observed 

 them make the slightest attempt to crawl, though he 

 frequently noticed them adhering together in masses, 

 attached by the anterior part of the foot, which acted 

 as a sucker. 



Family— SCALARiro^ {The Wentle-traps). 



The Wentle-traps are very different-looking shells 

 from the Violet Snails, bet the arrangement of the 

 teeth in the animals is nearly the same. The shell 

 is spiral, turreted, with varices, or elevated longi- 

 tudinal ribs, on the whirls. The aperture is rounded, 

 entire, and exhibits scarcely any trace of a canal. 

 The operculum is horny, spiral, few-whirled. The 

 species are numerous, about one hundred species 

 being found recent, and an equal number having been 

 described as inhabitants of our globe at an earlier 

 period of its existence. 



The genus Scalaria, the " Wentle-trap " is the 



only one of the family, and the species ai'e chiefly from 

 the eastern tropical seas. China and the Philippine 

 islands harbour the greater number, but five species ara 

 natives of the British isles. 



THE EOYAL STAHUCASE or Wentle-trap, "la 

 vraie Scalata" {Scalaria pretiosa), is the most remark- 

 able and the most valuable of all. This shell, always 

 distinguished for its beauty, and once famous for the 

 enormous value set upon it by collectors, is a native of 

 the Chinese seas. It grows to more than two inches 

 in length, is conical, umbilicated, and twisted into a 

 loose spire, so that the whirls only touch each other by 

 their projecting ribs. It is of a pale yellowish colour, 

 with white ribs or varices. " The specific name given 

 to it by Lamarck" {pretiosa), says Mr. Broderip, "was 

 at one time well deserved on account of its rarity, and 

 the great price which a fine specimen would bring in 

 the market, especially when it exceeded two inches in 

 height; such a specimen has been sold in former days 

 for twenty-four hundred livres, or one hundred louis. 

 But these times are gone by ; the shell is no longer 

 rare, and good specimens only fetch shillings where 

 they once brought pounds. A very fine example still, 

 however, commands a considerable simi. That in Mr. 

 Bullock's museum, supposed to be the largest known, 

 brought £27 at his sale, and was in 1815 estimated at 

 double that value." Da Costa, in his " Elements of 

 Conchology," informs us that in 1753, "at the sale of 

 Commodore Lisle's shells at Longford's, four AVentle- 

 traps were sold for £75 12s. ; viz., first day, February 

 21, lot 96, one not quite perfect, £16 16s. ; third day, 

 lot 98, a very fine and perfect one, £18 18s.; fourth 

 day, lot 101, one for £16 16s.; sixth day, lot 83, one 

 for £23 2s. At the present day the value is very 

 much reduced. 



The animals of some of the species exude a purple 

 fluid when molested, and Montagu in his " British 

 Shells" has described the liquor discharged by the 

 common species of the Mediterranean, S. clat/irus. 

 As much can be procured, he says, from five indi- 

 viduals as is suflBcient, when mixed with a few drops 

 of spring water, to cover half a sheet of paper. The 

 colom' at first was very bright, and appeared for some 

 months unchanged by the action of the air or sun ; but 

 being exposed for a whole summer to the solar rays, 

 in a south window, they almost vanished. Like the 

 lanthina, just mentioned, this Scalaria has been sup- 

 posed by some naturalists to have been one of the 

 shells employed b}' the ancients to furnish the celebrated 

 Tyrian dye, but the same objections apply to it as to 

 the purple fluid of the lanthina. — See above. 



The remaining families of the Proboscidifera, 

 ActeonidcE, Cerithiopsidce, Pyramiclellidce, and Archi- 

 tectomidce (Solarium), are of no particular interest, and 

 BO v/e hasten on to the next sub-order. 



Sub-order III.— KOSTEIFERA. 



The Bostriferous mollnsca are equally numerous as 

 the Proboscidiferous ; but instead of being carnivorous 

 in their habits, they are essentially vegetable feeders. 



The animals have a moderate-sized head, with a more 

 or less elongated, produced, transversely-annulated 

 rostrum, which is furnished with contractile muscks 



