The spiral-shaped

testaceans are all similarly constructed, but
differ from one another, as has been said, in the way of excess or
defect (for the larger species have larger and more conspicuous
organs, and the smaller have smaller and less conspicuous), and,
furthermore, in relative hardness or softness, and in other such
accidents or properties. All the stromboids, for instance, have the
flesh that extrudes from the mouth of the shell, hard and stiff;
some more, and some less. From the middle of this protrudes the head
and two horns, and these horns are large in the large species, but
exceedingly minute in the smaller ones. The head protrudes from them
all in the same way; and, if the animal be alarmed, the head draws
in again. Some of these creatures have a mouth and teeth, as the
snail; teeth sharp, and small, and delicate. They have also a
proboscis just like that of the fly; and the proboscis is
tongue-shaped. The ceryx and the purple murex have this organ firm and
solid; and just as the myops, or horse-fly, and the oestrus, or
gadfly, can pierce the skin of a quadruped, so is that proboscis
proportionately stronger in these testaceans; for they bore right
through the shells of other shell-fish on which they prey. The stomach
follows close upon the mouth, and, by the way, this organ in the snail
resembles a bird's crop. Underneath come two white firm formations,
mastoid or papillary in form; and similar formations are found in
the cuttle-fish also, only that they are of a firmer consistency in
the cuttle-fish. After the stomach comes an oesophagus, simple and
long, extending to the poppy or quasi-liver, which is in the innermost
recess of the shell. All these statements may be verified in the
case of the purple murex and the ceryx by observation within the whorl
of the shell. What comes next to the oesophagus is the gut; in fact,
the gut is continuous with the oesophagus, and runs its whole length
uncomplicated to the outlet of the residuum. The gut has its point
of origin in the region of the coil of the mecon, or so-called
'poppy', and is wider hereabouts (for remember, the mecon is for the
most part a sort of excretion in all testaceans); it then takes a bend
and runs up again towards the fleshy part, and terminates by the
side of the head, where the animal discharges its residuum; and this
holds good in the case of all stromboid testaceans, whether
terrestrial or marine. From the stomach there is drawn in a parallel
direction with the oesophagus, in the larger snails, a long white duct
enveloped in a membrane, resembling in colour the mastoid formations
higher up; and in it are nicks or interruptions, as in the egg-mass of
the crawfish, only, by the way, the duct of which we are treating is
white and the egg-mass of the crawfish is red. This formation has no
outlet nor duct, but is enveloped in a thin membrane with a narrow
cavity in its interior. And from the gut downward extend black and
rough formations, in close connexion, something like the formations in
the tortoise, only not so black. Marine snails, also, have these
formations, and the white ones, only that the formations are smaller
in the smaller species.