344 IjiPiiRATOKiNA. MOLLUSCA. Haliotid^. 
quantities under the name of “ Snail mother-of-pearl.” 
De Montfort tells us that he has seen a necklace formed 
of the nacred part of the Turbo smaragclus, much more 
brilliant and beautiful than any of the finest orient 
pearls. — (Johnston.) 
Gkoup II. — Imperatorina {Sun-troclmses). 
In this group the body 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 Imperator is the type. The shell of 
Imperator is trochiform, thick, with a flat or concave 
base, and keeled or stellated whirls. The species of 
Imperatorina number between twenty and thirty, and 
are all from tropical climates. — See Plate 3, fig. 1 
(Imperator gibber ulus). 
Group III. — Phasianellina {Pheasant shells). 
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 Phasianella (= Eutropia ). — This genus, 
so called because of the beautiful pheasant-like disposi- 
tion of the colours on the shell, is the typical one. — 
See Plate 3, figs. 4, 5 (Phasianella Australis and oper- 
culum). 
Family — TROCHIDj3]1 (Hoop-shells). 
The Hoop-shells, with the animal nearly the same 
as that of the Turbinidae, 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 fiat 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 Trochus 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 Trociiiscus. — This germs 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 columella, and smooth 
whirls, covered with an epidermis. 
T. KOREIsn, 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 
I'emarkable for having the outer edge of each spiral 
volution free and membranous, with the margin curled. 
Genus Delphinula (= Angarus ). — This genus 
has a depressed shell, orbicular in form, and umbili- 
cated. The whirls are few in number, angulated, 
rugose, 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 Red Sea. 
Genus Elenchus. — This genus has a turreted, 
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 — SCISSURELLID.^ (Little Slit-shells). 
The Little Slit-shells, though containing only one 
genus, ScissURELLA, and eleven species of very small 
and insignificant-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 in Norway, 
off the Orkneys in seven fathoms, and in deep water to 
the east of the Shetland isles. They are also found in 
the Mediterranean. 
Family — HALIOTIDEE (Ear-shells). 
The Ear-shells are much larger, and are a great deal 
more numerous, than the preceding family. The shell 
is ear-shaped, 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 fiat spire, a 
very wide and in many cases a highly-beautiful and 
iridescent aperture. The left side is characterized by 
a spiral ridge with a series of round holes in front, which 
become gradually filled up behind as new ones are 
