3 66 THE BEAKED SPINDLE-SHELL. 



circumscribed to admit even a tithe of the important existing species, no space can be 

 found for the fossils. It must, therefore, suffice in the present instance to remark that 

 the well-known ammonites, rams'-horns, and other similar fossil shells, belonged to the 

 same order as the Chambered Nautilus. 



The color of the shell is very beautiful. The ground is white, over which are drawn, 

 as with single dashes of a painter's brush, sundry bold streaks of reddish chestnut, 

 mostly coalescing above, and reaching nearly to the centre of the spiral. This porce- 

 lain-like material is, however, only an outer coat laid on the real pearly substance of 

 the shell, which is seen on looking into the hollow or into any of the chambers. The 

 Chinese avail themselves of this double coating, and, with the untiring perseverance of 

 their laborious nature, take the greatest trouble to spoil the finest shells, by covering 

 them with their grotesquely unperspective carvings of figures and landscapes, cut so as 

 to relieve the deep color of the raised figures by the white pearly background. Unlike 

 the shell of the argonaut, which is almost as fragile as if made of sugar, that of the 

 Nautilus is firm and strong, and will bear a considerable amount of rough handling 

 before betraying any signs of injury. 



WE now take leave of these highly developed molluscs, and pass to another order 

 where the organization is not nearly so perfect, and where the habits are either so common- 

 place as to be devoid of general interest, or the animals so shy that they never can be seen 

 performing any act which is likely to attract the attention of an unprofessed naturalist. 



The last order of molluscs are named cephalopods, because their feet surround their- 

 head. The order which now comes before our notice is composed of animals which 

 crawl upon a broad muscular organ, termed, from its use, the foot. It is an enormously 

 large order, containing all the snails, whether terrestrial, aquatic, or marine, the whelks, 

 limpets, and similar animals not so familiarly known. Many species are much used as 

 food, while others are of great service in the arts, furnishing employment to many hun- 

 dreds of workmen. As the shell of these creatures consists of one piece or valve only, 

 they are sometimes termed univalves, in contradistinction to the oysters, muscles, 

 scallops, and similar shells, which are termed bivalves, in allusion to their double shell. 



Passing by, for the present, the mere anatomical peculiarities of these creatures, and 

 leaving them to be mentioned in the table of Generic Differences at the end of the 

 volume, we will proceed at once to our first example of the gasteropods, the BEAKED 

 SPINDLE-SHELL, so called from the rather distant resemblance which its long and pointed 

 form bears to a spindle, and the elongated beak-like process which is seen pointing 

 downwards to the ground as the animal walks along. The right-hand figure represents 

 the Beaked Spindle. In the family to which this mollusc belongs, the lip of the shell 

 is always extended and'deeply notched. 



The animal possesses large and well-developed eyes, set on stout and moderately 

 long footstalks, from each of which a small tentacle proceeds. The foot is small, and 

 not well calculated for crawling, but more adapted for the abrupt leaping style in which 

 these animals proceed, their weighty shell swaying from side to side in rather an awk- 

 ward manner. 



There is a structure belonging to these animals which must be described before pro- 

 ceeding further, inasmuch as its shape and comparative dimensions often afford valuable 

 indications by which a species, or even a genus, may be distinguished. This structure 

 is called the " operculum," and its use, when fully developed, is to close the aperture 

 of the shell, when the animal has withdrawn itself into the recesses of its home. 



The operculum can be well seen in the water-snails, where it attains its full size, and 

 exactly fits the opening which it is intended to protect. The material of which the 

 operculum is essentially composed is a horny substance, but in some species the horn 

 is strengthened by layers of the same nacreous matter which lines the shell, and be- 

 comes so thick and heavy that, when found separate from its owner, it is often mis- 

 taken for some species of shell. The operculum is very variable both in its form and 

 comparative dimensions, and even in its presence or absence. Sometimes it is circular, 

 like a flat plate, and composed of concentric circles, while in some species it assumes 

 a regularly spiral form, like a flattened watch-spring. 



