THE EAR SHELL. 



215 



TROCHUS N1LOTICUS. 



TROCHUS VIRGATUS. 



Genus Trochns.* The shells of this genus are pyramidal, with a nearly flat base, the whorls are 

 variously striated, the aperture is squarish and pearly inside, the outer lip is thin, the operculum is 

 composed of many convolutions. There are 150 known and described species of this world-wide shell, 

 extending from low water to more than 100 fathoms. 



Genus Elenchus. The shell in this genus is thick and polished, and there is usually a single 

 tooth at the fore part of the columella ; the aperture is vividly iridescent within, and the surface is 

 often ornamented with varied and beautiful 

 markings. This species is characteristic of 

 Australia ; fifteen have been described. They 

 are polished and worn by the natives of North- 

 east Australia as necklaces. 



Genus Rotella, "the Button-shell." The 

 shell is like porcelain, the whorls round and 

 polished, the base or umbilicus covered with a 

 large callosity, aperture small, outer lip acute. 

 The upper part of the shell is banded with lines 

 of colour. Eighteen species are recorded, from 

 India, the Philippines, China, and New Zealand. 



Genus Monodonta, the " Rosary-shell." It is top-shaped, like the common Periwinkle in form ; 

 the whorls are grooved and granulated spirally, lip thickened and grooved, columella irregularly 

 toothed, operculum whorled and horny. Ten recent species are known from West Africa, Red 

 Sea, India, and Australia. They inhabit mangrove swamps. 



Genus Delphi iinJa. The shell has few whorls, the apex is depressed, the angles of the whorls" 

 are rugose or spiny, the aperture is round and pearly within, the umbilicus is open, the operculum 

 horny and many-whorled. Delphinula is found living on coral reefs at low water. Twenty species 

 have been described, from the Red Sea, India, the Philippines, China, and Australia. 



Genus Cyclostrenia. This little shell differs from Delphinula in being nearly discoidal ; the 

 whorls are cancellated or cross-ribbed, and the inside of the shell is not pearly. Eighteen species are 

 recorded, living in five to twenty fathoms water, at the Cape, India, the Philippines, &c. 



Genus Stomatellfi. The shell has a minute spire and a very large oblique aperture ; the interior 

 is pearly ; lip thin and even ; operculum circular, horny, spiral. Twenty recent species are described, 

 from the Cape, India, Australia, &c. The genus Gena differs but little from the preceding one, save 

 in the absence of the operculum. Sixteen species have been described, mostly from the Philippine 

 Islands, where they appear to represent the genus Ho fit, fin. 



FAMILY XX. HALIOTID^E. 



This shell is ear-shaped and spiral ; the aperture is very large, pearly and iridescent within ; 

 perforated with a series of holes ; there is no operculum. 



The animal has a short broad head, with eyes on stout stalks at 

 the outer base of the tentacles ; the left lobe of the mantle elongated 

 into an anal siphon, occupies the anterior perforation of the shell ; 

 the foot is large, and very thick, with serrated lobes and filaments on 

 the outer edges. With the true Ear-shells (ffaliotidce) are placed such 

 of the Trochiform shells as have a notched or perforated aperture. 

 Genus Haliotis,^ ''Ear-shell." The shell has a small flat spire 

 and a very wide iridescent aperture ; exterior striated, corrugated, 

 and dull, often incrusted with corallines, &c. ; outer angle perforated 

 by a series of holes, which are successively closed. Seventy-five 

 living species are known ; they inhabit the littoral zone, and occur 

 in Britain, the Canaries, India, Australia, and California, &c. 



In the Ear-shell (Haliotis), found living on the rocks at low water in the Channel Islands and 

 elsewhere, and so common a mantelpiece ornament, on account of its pearly interior, the ex-current 

 * latin, trochns, a hoop. t Greek, halios, marine, and ous, an ear. 



HALIOTIS TKICOSTALIS. 

 (p) Perforation for syphon. 



