31 6 Cephalox’Oda. MOLLUSCA. Mautiliu.e. 
into the numerous cells of this siiell, thus at will vary- 
ing their proportionable weight to the sea in which they 
live; and M. d’Orbignj' is of opinion that the use of 
the proi linent mucro, or point, is to protect the animals 
in the frequent collisiotis they are exposed to in swim- 
ming backwards. The black liquid secreted by this 
species of Cuttle-lish is said to form at least the greater 
jiortion of the colour called sepia. Though now it is 
pretty well ascertained that the China ink of commerce 
is prepared from lamp-black or finely triturated char- 
coal, it was long believed to he fui-nished by this 
secretion ; and Cuvier tells us that an ink is still pre- 
pared from this secretion in Ital^q which only dift'ers, 
he sa3's, from genuine China ink in being a little 
less black ; and that it was with this preparation he 
drew the designs which illustrate his memoir on the 
Mollusca. The hone, as it is called, or shell of the 
Sepia, is much used in the preparation of tooth-powder 
and pounce. It was formerly employed by medical 
men as an antacid, but is now little esteemed for 
that purpose. It is of more value, when powdered, 
for making moulds for silversmiths for casting articles 
of small work, such as spoons, forks, and rings. 
Section III.-BELEMNOPIIORA. 
This section contains onl}' one recent family ; — 
Family— SPIRULIDxE (Spirulas). 
'Phese animals have an oblong body, with minute 
terminal fins. The sessile arms have six rows of veiy 
minute cups, and the tentacular arms are elongated. 
The shell is entirely nacreous, discoidal, with the whirls 
separate, and chambered, the chambers furnished with 
a siphon. The last chamber is onl}' large enough to 
contain a very small part of the animal ; the rest of the 
shell being placed vertically in the posterior part of the 
body, with the involute spire towards the ventral side. 
Plowever dissimilar, says Cuvier, this shell is in figure 
to the bone of the sepia, it does not differ much from 
it in the manner of its formation. “If we imagine 
that the successive layers, instead of remaining parallel 
and in nigh approximation, were to become concave 
towards the body, more distant, each growing a little 
in breadth, and making an angle between them, we 
should then have a very elongated cone, rolled up 
spirally on one plane, and divided transversely into 
chambers. Such is the shell of Spirula, which has 
these additional characters, that the turns of the spire 
do not touch, and that a single hollow column, occu- 
pying the interior side of each chamber, continues 
its tube with those of the other columns even to the 
extremity of the shell. This is what is named the 
Siphon." 
Genus Spiuula {=Lituus). — The family contains 
only this one recent genus. Though tlie shell of 
Spirula has long been well known, specimens of one 
of the species being often found brought by the gulf 
stream, and thrown up on the shores of our own 
country, and thousands of them scattered along those 
of New Zealand, yet the animal has been very seldom 
seen. An imperfect specimen was brought home some 
years ago by Captain (now Admiral) Sir E. Belcher, 
and served Professor Owen as the rpecimen from which 
his memoir on the anatomy of the creature was drawn 
up ; and more recently a nearly perfect specimen of 
another species has been found by Mr. Earl off the 
coast of New Zealand, which is now in the possession 
of Mr. Cuming, and was figured b}' Mrs. Gray in the 
Annals of Natural History, vol. xv. From the little 
we know of its habits, it is most probable that the 
Spirula is pelagic, and swims near the surface in calm 
weather towards evening, preying on acalephie, and 
sinking below the surface during the day. Three 
species have been described. 
Okder II.— TETKABRANCHIATA. 
The animal in this order of Cephalopods creeps instead 
of swims, and has its body protected hj'- a shell. The 
body is destitute of fins, and is attached to the shell 
(unlike that of Argonauta) by adductor muscles, and | 
by a continuous horny girdle. The head is retractile 
within the mantle, is not separate from the body, and 
is siUTOunded bj' a great number of C 3 'lindrical, annii- 
lated, retractile tentacles, destitute of suckers. The 
eyes are slightly pedicelled, the mandibles are calcare- 
ous, the siphnncle, or funnel, is slit ; and, as the name 
of the order indicates, they have four gills or branchiae. 
The shell is external, chambered, and is provided with 
a siphnncle. “The inner layers and septa are nacre- 
ous, and the outer layers porcellaneous.” — Woodward. 
This order contains three families, only one of which, 
however, possesses an3' recent si)ecies. i 
Family— NAUTILIDZE [The Nautili). 
I This family contains hut few living representatives, 
but in former periods of the earth’s history they 
appear to have been extremel3' numerous. 
Genus Nautilus. — This is the only genus belonging 
to the family. The tentacles which surround the head 
of the animal are very numerous. On each side of the 
head there is a double series of arms or brachial tentacles, 
as they are called, thirty-six in number, lamellated on 
their inner surface, and retractile within sheaths or digi- 
tations which correspond to the eight ordinary arms of 
the Dibranchiate species. There are also four groups of 
labial tentacles, twelve or thirteen in each group, which 
I apiiear to answerto the buccal membrane of the ordinai y 
