18 SHELL GALLERY. 



are almost exclusively found in tropical or subtropical regions, 

 the majority being met with either at low-water mark or in com- 

 paratively shallow water. 

 r Case 5, The " Volutes " ( Volutidce) are a group of shells also much 

 C ~ F, J sought after by shell- collectors. Some of these attain to a very 

 large size, the animals inhabiting them being enormous. The 

 Boat- shells (Cijmba) and Melons (Cymbium) are ovo-viviparous, the 

 young being carried about by the parent until they are an inch in 

 length. Volutes are found chiefly in the warmer parts of the 

 Atlantic and Indo-Pacific Oceans, and occur in the greatest variety 

 on the coasts of Australia. 

 [Case 5, The "Helmet-shells'" {Cassididae) are used for cameo-carving; 

 C_H, J they consist of differently coloured layers, so that the ground- 

 colour of the carving is of a different tint from the subject engraved. 

 The most artistic shell-cameos are produced in Italy, whence the 

 art has been introduced into France and England. The Cassis 

 madagascariensis is in special request by shell-carvers on account 

 of the strong contrast of the white upper layer with the dark ground 

 beneath. Extinct forms of Cassis are found fossil in Tertiary for- 

 mations, but none of them equal in size the largest living species. 

 [Case G, The " Tun-shells " (Doliidce) are remarkable for the globoseness 

 A-D of the shells, which are covered with very regular revolving ribs. 



The "Trumpet-shells" (Tritunida:) have varices or strengthening 

 ribs at intervals, like the Murices; the largest species, Triton 

 variegatus, is used by South- Sea Islanders as a horn or trumpet. 

 A hole is made in the upper part of the spire to blow through, 

 and the sound produced can be modulated or varied by inserting the 

 hand in the aperture or mouth of the shell. 

 [Case 6, This case contains the " Fig-shells" (Ficula), the Natica, the 

 d-h.] « Violet Snails " (lanthinas), the " Wentle-traps " (Scalariida), 

 and the Solarium s or " Perspective-shells." The Naticas are 

 mostly blind, and have a very large foot, suitable for burrowing in 

 the sand when in quest of bivalves. They are very voracious. 

 This is one of the groups of shells that have continued to exist from 

 Palseozoic times. 



The Scalaria pretiosa was formerly considered a great rarity, 

 as much as £40 having been given for a single specimen, which 

 might now be purchased for as many pence. The " Violet Snails " 



