THE BLACK OLIVE. 3 8i 



JUST below the needle-shell is seen the beautiful SPOTTED IVORY-SHELL, also a 

 native of the hotter latitudes. 



Few species, not more than eight or nine in number, are known to exist at the 

 present day. They are all very smooth and polished on the exterior, and their sub- 

 stance is so thick and solid that they seem almost to be made of earthenware. They 

 reside at a moderate depth, being generally found in twelve or fourteen fathoms of 

 water. It is worthy of notice that the rich spotted markings of the shell are repeated 

 upon the body of the animal. The members of this genus possess tolerably large eyes, 

 set at the base of the long tentacles. As in the preceding genus, the operculum has 

 its nucleus at the pointed end. 



The color of the Spotted Ivory-shell is pure porcelain-white, richly spotted with 

 deep brownish red, something like the tint known to artists as burnt sienna. It is not 

 a very large shell, being about two inches in length. 



THE last figure, with occupies the extreme left of the illustration, represents the 

 APPLE TUN-SHELL, one of a moderately strong genus, deriving their popular name from 

 the rounded and barrel-shaped outlines of the shell. 



The animal is shown as it appears when crawling, for the purpose of exhibiting the 

 curious striped edges of the feet, and the manner in which the siphon is carried bent 

 over the front of the shell like the uplifted proboscis of an elephant. In these shells 

 the spire is comparatively small and short, and the aperture very large, thus producing 

 a great contrast to the needle-shell on the same engraving. About fourteen species of 

 Tun-shells are known, all inhabiting the warmer seas. 



The color of the Apple Tun-shell is nearly white, diversified here and there with a 

 few spots of the palest saffron. The interior, however, is much more deeply colored 

 than the outside, being of a rich yellow with a slight dash of orange. 



THE beautiful HELMET-SHELLS also belong to this useful family. Several of these 

 shells are employed by the engravers in the manufacture of cameos, the differently 

 colored layers producing most exquisite effects when cut by a judicious operator. The 

 colors vary greatly in the different species, and sometimes there is a slight variation 

 even in different individuals belonging to the same species. Cameos, for example, 

 that are cut from the HORNED HELMET-SHELL (Cassis corm'ita) are white, upon aground 

 of rich orange ; those that are made from the WARTY HELMET-SHELL (Cassis tuberbsd) 

 are white, on deep dark red ; the cameos formed from the shell of the RUDDY HELMET 

 (Cassis rufa) are saffron-yellow on warm orange. Another beautiful species, called the 

 QUEEN CONCH (Cassis Madagascariensis], furnishes a white cameo on a claret-colored 

 ground. 



These shells are tolerably thick and solid, and their external surface is covered with 

 bold ridges, marking the periodical growth. These ridges are technically called 

 varices." All the Helmet-shells are natives of the tropical seas, and appear to prefer 

 the shallow waters near the coast. 



ON the extreme left of the next illustration is a dark smooth shell, represented as 

 crawling on the ground, and partially enveloped in the spotted textures of the living 

 creature. 



This is the BLACK OLIVE, so called on account of the jetty blackness of its exterior, 

 and the oval, rounded form, which is not unlike that of the fruit whose name it bears. 

 The genus Oliva is a very large one, comprising more than one hundred species, and 

 found in all the warm and tropical seas. As may be seen by the figure, the mantle is 

 furnished with two large lobes, that nearly meet over the back while the animal is 

 moving, and which throw out certain filamentary projections, that look very like ten- 

 tacles in the wrong place. The foot is very large so large, indeed, that the shell is 

 partly buried in its soft material and the eyes are, as may be seen in the figure, 

 placed before the middle of the tentacles. 



Owing, probably, to the great development of the foot and mantle, the Olives are active 

 creatures, gliding about with tolerable speed, burying themselves in the sand when the 



