344 



IjirEBATOEINA.- 



-MOLLUSCA.- 



-Haliotid.e. 



quantities under the name of " Snail motber-of-pearl." 

 Pe Montfurt tells us that he has seen a necklace formed 

 of the nacred part of the Turbo smaragdus, much more 

 hrilliant and beautiful than any of the finest orient 

 pearls. — {Johnston.) 



GiiOUP II. — Impeu.vtorina {Sun-trochnses). 



In this group the bod)' of the animal is subquadrate ; 

 the aperture of the shell is angulated outside, brilliantly 

 pearly within ; and the operculum is oblong or ovate. 



The genus Impekatok is the type. The shell of 

 Iraperator is trochiform, thick, with a flat or concaTe 

 base, and keeled or stellated whirls. The species of 

 Imperatorina number between twenty and thirty, and 

 are all from tropical climates. — See Plate 3, tig. 1 

 [Imperator gihberulus). 



Gnoup III.— PllASlANELLlNA {Pheasant shdb). 



This group is characterized by the body of the ani- 

 mal being ovate, and the aperture of the shell and the 

 operculum partaking of the same form. 



Genus Puasianella {=z Eutrojyia). — This genus, 

 BO called because of the beautiful pheasant-like di.sposi- 

 tion of the colours on the shell, is the typical one. — 

 See Plate 3, figs. 4, 5 {Phasianclla Australis and oper- 

 culum). 



Family— TROCHID^ {Hoop-shells). 



The Hoop-shells, with the animal nearly the same 

 as that of the Turbiiiidaj, have a horny operculum, 

 thin, not covered with a calcareous coat, orbicular, and 

 composed of many gradually enlarging whirls. — (See 

 Plate 3, fig. 2.) The shell is generally pyramidal in 

 shape, with a nearly flat base, and the last whirl more 

 or less angulated at the circumference. The aperture 

 is contracted and of a quadrangular shape, pearly inside, 

 and with a thin outer lip. The columella is twisted, 

 slightly truncated.— (See Plate 3, fig. 1, 3, 4.) 



Fig. 223. 



Trochus niloticus and operculum. 



The genus Tkochds is the typical one of the 

 family ; and the Nilotic Trochus, Trochus niloticus, 



perhaps the largest, and one of the handsomest species 

 of the whole family, will illustrate the genus (see fig. 

 annexed). 



Genus Trochiscds. — This genus is remarkable, 

 and only distinguished as belonging to this family by 

 its operculum. It has a widely umbilicated shell, 

 with an obtuse spire, a simple cohmiella, and smooth 

 whirls, covered with an epidermis. 



T. NOREISn, the only species, is extremely like a 

 species of Turbo, and might be considered as belong- 

 ing to that genus, were it not for its operculum. This 

 is horny, of many gradually enlarging whirls, and is 

 remarkable for having the outer edge of each spiral 

 volution free and membranous, with the margin curled. 



Genus Delpiiinui.a (= Angarus). — This genus 

 has a depressed sliell, orbicular in form, and umbili- 

 cated. The whirls are few in number, angulated, 

 rugo.se, or spiny ; the aperture is round, pearly within, 

 and the peristome is continuous. The species are of 

 tolerable size, about twenty in number, and are distri- 

 buted through the warm seas of India, the Philippines, 

 China, Australia, and the Reil Sea. 



Genus Elenchus. — This genus has a turretcd, 

 smooth, and polished shell, with rounded whirls and 

 no umbilicus. The aperture is ovate, and brightly 

 pearly within, and the pillar lip has a single more or 

 less produced tooth in front. The whole shell, when 

 the outer layer has been removed, is of a fine pearly 

 iridescent hue ; and several of the species, which are 

 all Australian in their geographical distribution, are 

 used by the natives about Bass' Straits and Flinder's 

 Island, when strung together, as bracelets and neck- 

 laces. 



Family- SCISSURELLIDiE {Little Slit-shells). 



The Little Slit-shells, though containing only one 

 genus, Scissukella, and eleven species of very small 

 and insigniticant-looking shells, has many representa- 

 tives — in a fossil state — of a former period, but much 

 larger in size. The shell is spiral, of very small size, 

 depressed, transparent, and widely umbilicated; the 

 whirls are keeled, the aperture rounded, and the outer 

 lip has a slit or narrow fissure in the margin ; the oper- 

 culum is thin, horny, and circular. The species are 

 natives of the northern seas, being found iu Norway, 

 oft" the Orkneys in seven fathoms, and in deep water to 

 the east of the Shetland isles. They are also found in 

 the Mediterranean. 



Family— HALIOTID^ {Ear-shells). 



The Ear-shells are much larger, and are a great deal 

 more numerous, than the preceding family. The shell 

 is ear-sliaped, with a very large and finely nacred 

 aperture ; and the outer lip is perforated with a series of 

 holes over the mantle fissure. There is no operculum. 



Genus Haliotis, or Ear-shell. — This genus has 

 has a depressly ovate shell with a small flat siiire, a 

 very wide and in many cases a highl3'-beautiful and 

 iridescent aperture. The left side is characterized by 

 a spiral ridge with a series of round lioles in front, which 

 become gradually filled up behind as new ones are 



