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THE STAIRCASE, OR PRECIOUS WENTLETRAP. 



IN tke family of the Turritellidse, the shell is either tubular or spiral ; the aperture is not 

 waved, notched, or formed into canals ; the foot- is very small, the muzzle is short, and the 

 eyes sunk rather deeply into the base of the tentacles. 



The COMMON TURRITELLA is a species belonging to the typical genus of this family. 



In all the Turritellas the shell is long, pointed, and with many whorls ; the aperture is 

 rounded and its edge thin ; the operculum is horny and with many whorls, and with a slightly 

 fringed edge. About fifty species of these shells are known, spread over the whole world, and 

 inhabiting the moderately deep waters of the shores, ranging from a depth of one to fifty 

 fathoms. They are supposed to be carnivorous. The color of the Common Turritella is whitish. 



THE curious WORM-SHELL, which derives 

 its name from its long and twisted form, is 

 a very remarkable shell, and, if carefully exam- 

 ined, affords much instruction as to the mode 

 in which the mollusks build up their wonderful 

 homes. It looks, indeed, much as if it were iu 

 the preliminary stage of shell-making, and had 

 completed its arrangements with the exception 

 of pressing the whorls together. When young, 

 the spiral form is tolerably regular, but as it 

 grows in years its regularity decreases, and the 

 shell exhibits the form represented in the 

 engraving, in which the figure is somewhat 

 magnified. 



The aperture of the Worm-shell is round, 

 and the operculum is consequently circular, and 

 fits the opening with tolerable closeness. Its 

 open, the tube is found to be supplied with many 

 The color of the Worm-shell is grayish-yellow. 



WORM-SHELL. Vermetus lumbiicali*. 



external face is concave. When not 

 partitions of the same material as its walls. 



A SHELL of somewhat similar construction, but readily distinguishable by the longitudinal 

 slit which extends throughout its entire length, is called the SNAKE-SHELL. About seven 

 species of the Siliquaria are known, all of which are carnivorous in their habits, and are found 

 within sponges. As in the last species, the Snake-shell is regularly spiral at its commence- 

 ment, where it was constructed by the animal in its youth, but loses its regularity in exact 

 proportion to its age. Its color is whitish. The small head, when just protruding, exhibits 

 the stopper-shaped operculum. 



THE shell of the STAIRCASE, or PRECIOUS WENTLETRAP, was in former days one of the 

 scarcest and most costly of the specimens of which a conchologist's cabinet could boast. There 

 was hardly any sum which a wealthy connoisseur or virtuoso, as the fashion was then to call 

 those who were fond of natural history, would not give for an especially large and perfect 

 example of this really pretty shell. Now, however, its glory has departed, for a tolerably good 

 specimen may be procured for a very small amount, and a Wentletrap which would twenty or 

 thirty years ago have been sold for two hundred and fifty dollars, can now be purchased for 

 less than one dollar. 



Putting aside, however, the question of rarity or cost, this shell is a very interesting one, 

 both for its beauty and the mode of its construction. It is purely white and partly transparent, 

 the elevated ridges being of a more snowy white than the body of the shell, on account of their 

 superior thickness, which does not permit the light to pass through them as in the case of the 

 thinner body. The whorls of this shell are separate, from each other, and apparently bound 

 together only by the projecting ridges, so that the general appearance is as if the whorls of a 

 worm-shell had been pressed nearly together, and then kept in their place by a succession of 

 shelly elevations. This beautiful shell is found in the Indian and Chinese seas. 



