326 THE STAIRCASE, OR PRECIOUS WENTLETRAP. 
In the family of the Turritellide, 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 WorRM-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 in 
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 
external face is concave. When not open, the tube is found to be supplied with many 
partitions of the same material as its walls. The color of the Worm-shell is grayish-yellow. 









































WORM-SHELL.— Vermetus lumbricalis. 
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 mgularly 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 protfuding, exhibits 
the stopper-shaped operculum. 
Tue shell of the SratrcAsE, or Prectous 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 cail 
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-shel] 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. 
