368 



THE COMMON SPIDER-SHELL. 



overlapping each other like the tiles of a house, or the successive steel layers of a 

 carriage-spring. 



Some species of Strombs attain a considerable size, and are much used in the arts, as, 

 for example, the GIANT STEOMB, or FOUNTAIN SHELL (Strombus gigas), one of the West 

 Indian species, which sometimes attains the weight of four or five pounds, and is 

 imported into Europe in several thousands for the use of engravers, who cut the well- 

 known cameos from its beautifully tinted substance. Three hundred thousand of these 

 shells were brought to Liverpool alone in a single year. As the animal increases in age, 

 it gradually fills up the hollow apex and spines with solid matter, and thus materially 

 adds to the weight of the shell without improving its value to the engraver. In some 

 parts of the world, such as Barbadoes, the Giant Stromb is eaten, and sold regularly for 

 that purpose. Pearls of a delicate pink colour have sometimes been found in this shell, 

 but their occurrence is not frequent, probably on account of the careless and unobservant 

 habits of the negroes who clean the shells. Pearls are also found in other species 

 belonging to this genus. 



The teeth of the Strombs are extremely beautiful and most complicated, but cannot 

 well be described without the aid of illustrations. 



The colour of the Three-horned Stromb is brown and yellow of different shades, richly 

 mottled with pale saffron. Its average length is about four inches. 



COMMON SPIDER SHELL. Fterdcems lumbit. ORANGE- MOUTHED SPIDER-SHELL. Pterocerua u.ura>,.tvu 



THE two species represented in the illustration derive their popular names from the 

 generally spider-like contour of their form. 



When adult, the outer lip is furnished with several horny appendages, always curved, 

 and not precisely of the same shape in the same species, although the general character of 

 their form is sufficiently well marked to distinguish the species. One of these horns is 

 always close to the spine, and is rolled in such a manner as to form a posterior canal. 

 About ten species of these animals are known, and seem to be confined to the Chinese and 

 Indian seas. 



The COMMON SPIDEE-SHELL is seen on the left of the illustration, the animal being 

 represented in the act of crawling, the foot being applied to' the ground, the operculum 

 trailing behind, and the two eyes in their long footstalks projecting in front. The colour 

 of this shell is very handsome, consisting of boldly mottled chestnut, like the hue of 

 old rosewood, variegated with white, and traversed by lines of orange. The interior of the 

 shell is pale brown, with a dash of yellow. The average iength is three or four inches. 



