Vermetid^.- 



-MOLLUSCA.- 



-Stkombid.e. 



341 



Family— VERMETID^ (The Worm-slielh). 



The aiiiraals of this family have a very small rudi- 

 mentary foot, not serving for locomotion. It is folded 

 on itself, and is truncated or clnb-shaped in front. 

 The body of the animal is irregularly twisted, as is also 

 the shell, which is tubular, and attached by its side. 

 The opercidum is spiral, horny, and circular, when 

 present, but it is sometimes wanting. The eggs are 

 contained in an oblong membranaceous sac, and the 

 yuung shells are subsiiiral, rather irregular. 



Genus Siphoniuji. — This genus, which contains the 

 largest species of the family, has the operculum very 

 large, smooth, circular, and concave, with the scar 

 central. The shell, which is tubular, is usually fixed, 

 and the whirls are always irregularly twisted when 

 adult, and often carinated. The aperture is round. 

 In conseqnence of the shells of this family being always 

 fi.xed or attached to other bodies, the animals are 

 unable to crawl or glide along; hence the reason of the 

 smallncss of the foot. 



Genus Vermetcs. — This genus Jiflfers chiefly from 

 the preceding by the whirls of the large, rather con- 

 cave operculnm, liaving a thin, produced, external edge. 

 In Vennetiis radicnla, a North American species, it is 

 horny, black, and bard on the inner, and lamellated on 

 the outer surface. It is surrounded by a thin, mem- 

 branous, flexible portion, about one-fourth its diameter; 

 thus it is enabled to close its shell perfectly at the 

 aperture, and yet to retreat far into the narrowed 

 whirls. — [Gray.) The shell of the young animal, before 

 it escapes from the egg, appears to be helicoid and 

 reversed ; bnt, when adult, is irrcgidarly twisted, the 

 whirls more or less disunited, and the last generally 

 prolonged. 



GfNUS SiLlQUARlA. — In this genus the operculum 

 is many-whirled, spiral, and fringed. The shell is 

 tubular, internally glossj', and irregularly twisted. 

 The apex is attenuated, sometimes spiral, and a longi- 

 tudinal fissure runs throughout its whole length. The 

 species are often found in sponges. 



In the next two families, Strombid(E and PJioridcc, 

 the animals are distinguished by their having the foot 

 compressed, and adapted for leaping instead of crawling. 

 The gills are comb-like, and placed on the left side of 

 the mantle cavity. 



Family— STROMBID^( r/ie&romi or Wing-sheVs). 



The species of this family have a solid spiral shell, 

 with compressed whirls and a linear aperture. The 

 outer lip changes its form with age, becoming, when 

 adult, more or less expanded, and either simple and 

 entire at the fore part, or deeply notched. The oper- 

 culnm is annular, horny, claw-shaped, and serrated on 

 the outer side. The Strombs are active, muscular, and 

 predaceous animals, using their operculum as a weajion 

 of defence. Their eyes are well developed, having 

 both pu[iil and iris, the latter often beautifully coloured. 

 The crystalline lens is large, perfectly globular, and 

 horn-coloured. " The perfect development of the large, 

 fine, pedunculated eyes of Strombus," says Mr. A. 



Adams in bis "Voyage of the Samarang," "together 

 with its very elongated, powerful, muscular body and 

 foot, and claw-shaped, stout, jagged, liorny operculum, 

 constitute it one of the most active and intelligent of 

 Molluscs. It is, in fact, a most sprightly and energetic 

 animal, and often served to amuse me by its extraor- 

 dinary leaps and endeavours to escape, planting firmly 

 its powerful narrow operculum against any resistiiig 

 surface, insinuating it under the edge of its shell, and 

 by a vigorous effort throwing itself forwards, carrying 

 its great heavy shell with it, and rolling along in a 

 series of jumps in a most singular and grotesque man- 

 ner." The Rev. Lansdowne Guilding affirms that they 

 jiossess the sense of hearing also, or something allied 

 to it. 



Genus Strombus. — In this genus the aperture of 

 the shell is lengthened, narrow, notched, or having a 

 sliort canal in front, and channeled posteriorly, and the 

 expanded outer lip is often lobed and deeply notched 

 in front near the canal. In the young state, however, 

 the shells present a very dilTerent appearance, resembling 

 somewhat an ill-formed cone. The species are numer- 

 ous, upwards of sixty having been described. They 

 are pretty generally distributed, but are by far more 

 numerous in tropical seas than in those of temperate 



strombus Isabella, witli animal and eye. 



countries. They are found on reefs at low water, and 

 ranging to ten fathoms. The genus is represented by 

 the Strombus Isabella (fig. 221). 



THE GIANT STEOMB, or FOUNTAIN Shell of tho 

 West Indies {Strombus 0>gas), is one of the largest 

 living shells, weighing sometimes four or five pounds. 

 The animal is occasionally used as an article of diet, 

 and the shell is extensively used in the manufacture of 

 cameos. Immense quantities are annually imported 

 from the Bahama islamls for this purpose, and for 

 porcelain works. In 1850 three liundred thousand 

 shells were imported to Liverpool alone. 



Genus Pteroceua. — The Scorpion Sfiells. as they 

 are called, are characterized by the shell having au 



