Mollusca. the last cell produced into a tube. 
=~’ of this terminal tube are unknown. 
MOLLUSCA. 
The position and use 
The S. vulgaris is the 
most common species, and inhabits the seas in the West 
Indies. In the restricted genus Nautilus, the shell is sup- 
posed to be external, and the body of the animal to be lodg- 
ed in the last chamber, and to be fixed by a ligament which 
descends into the central pipe. In the shell itself, the turns 
of the spire are contiguous, and the last whorl embraces the 
others on the sides. The WV. Pompilus of Rumputts is the 
only species in which the animal has been detected. 
The other genera which have been formed in this order 
depend exclusively on the characters furnished by the shells ; 
and the resemblance which these bear to the preceding 
genera, constitutes all their claim to be included in the pre- 
sent order. 
x Orver II.—Srpiacna. 
Destitute of a multilocular shell. 
The sac is strengthened by horny or testaceous plates, 
unless where the habits of the animal render such support 
unnecessary. 
1. Head surrounded with eight arms and two feet. 
The two feet are nearly similar in their structure to the 
arms, or tentacula, but considerably larger in their dimen- 
sions. They have their origin on the ventral side of the 
mouth, between that organ and the funnel. The suckers 
are pedunculated, with their margin strengthened by a corn- 
eous ring, furnished with teeth. The sac is furnished with 
fin-like expansions, and strengthened internally by corneous 
or testaceous ribs or plates. The head is divided from the 
sac on all sides by a neck. The margin of the anus is sur- 
rounded with tentacula. 
Gents Serra. The sac is furnished on each side through- 
out its whole length with a narrow fin. 
The suckers are irregularly scattered cn the arms and 
feet. The back is strengthened by a complicated calca- 
reous plate, lodged in a peculiar cavity. This plate has 
been long known in the shop of the apothecary under the 
name Cuttle-fish bone, which was formerly much prized in 
medicine as an absorbent, but is now chiefly sought after 
for the purpose of polishing the softer metals. It is some- 
what ovate, flatly convex on both sides, and thickest where 
broadest. The superior half, or the one next the head, is 
the longest, rounded at the extremity, and thin. The in- 
ferior portion becomes suddenly narrow, and ends in a point. 
It may be considered as consisting of a dermal plate, con- 
cave on the central aspect, having its concavity filled up 
with layers which are convex on their central aspect. 
According to our observations, the dermal plate appears 
to consist of three different lamine, arranged parallel to one 
another. The external or dorsal layer is rough on the sur- 
face, and marked by obscure, concentric arches towards 
the summit, formed by minute knobs, which become larger 
towards the base, where they appear in the form of inter- 
rupted transverse ridges. It is uniform in its structure, and 
the tubercles possess a polish and hardness equal to porcel- 
laneous shells, although they blacken speedily when put 
in the fire, and contain a good deal of animal matter. On the 
central side of this layer there is one flexible and transpa- 
rent, similar to horn, and smooth on the surface. The third 
layer is destitute of lustre ; and, in hardness and structure, 
resembles mother-of-pearl shells. 
The layers which fill the concavity of this dermal plate 
are slightly convex on the central aspect, and are in part 
imbricated. ach layer is attached to the concave surface 
of the dermal plate, by the upper. extremity and the two 
sides, while the inferior or caudal extremity is free. The 
inferior and first formed layers are short, occupy the base 
and middle, and rise from the plate under a more obtuse 
VOL. XY. 
353 
angle than the new formed layers, which are both the long- Mollusca. 
est and the broadest. 
Each layer, which is about one-fiftieth of an inch in dia- 
meter consists of a very thin plate, the dermal surface of 
which, when viewed with a magnifier, exhibits numerous 
brain-like gyrations. From the ventral surface of this plate 
arise numerous perpendicular laminze, which, when viewed 
laterally, appear like fine parallel threads, but when examin- 
ed vertically, are found to be waved, and fold upon them- 
selves. Next the plate they are thin, and not much fold- 
ed; but towards their other extremity they become thicker, 
striated across, and more folded, with irregular margins. 
On the thick, tortuous even ends of these laminz, the suc- 
ceeding plate rests, and derives from them the peculiar 
markings of its surface. These lamine are closely set, ir- 
regularly interrupted, and occasionally anastomose. M. 
Cuvier states, erroneously, (Mém. sur la Seiche, p. 47.) 
* that these lamina: are hollow pillars disposed in a quincunx 
order. 
The term done has been improperly applied to this com- 
plicated plate ; “for,” according to Mr. Hatchett, (Phil. 
Trans. vol. \xxxix. p. 321.) “ this substance, in composition, 
is exactly similar to shell, and consists of various mem- 
branes, hardened by carbonate of lime, without the small- 
est mixture of phosphate.” 
The most remarkable species of this genus is the Sepia 
officinalis, which is distinguished from the others by its 
smooth skin. It inhabits the British seas, and although 
seldom taken, its bone is cast ashore on different parts of 
the coast, from the south of England to the Zetland isles. 
Genus Louico. Calamary. Sides of the sac only fur- 
nished partially with fins. 
The suckers are disposed on the arms and feet ina 
double row. The dorsal plate is flexible and corneous, im- 
bedded in the substance of the sac, and is multiplied with 
years. Dr. Leach has described three new species of the 
genus Loligo, which were collected by Mr. Cranch during 
the voyage to the Congo, in that unfortunate expedition 
under the direction of Captain Tuckey. These species be- 
long to a group which have the suckers produced into hook- 
ed processes. In two of these species, Z. leptura and 
Smithiz, the suckers on the arms, as well as the feet, are 
produced into hooks, while, in one species, L. Banksid, the 
feet only are armed with hooks. 
The same distinguished naturalist has instituted a new 
genus nearly allied to Loligo, from two species collected 
during the same voyage. The following characters are as- 
signed to it. 
“ Genus Crancuta.—Body oval, sac-shaped; fins ap- 
proximating, their extremities free; neck with a frenum 
behind, connecting it with the sac, and with two other 
frena, connecting it with the sac before. 
“Sp. 1. Cranchia scabra—Sac rough, with hard, rough 
tubercles. 
“ Sp. 2. Cranchia maculata—Sac smooth, beautifully 
mottled with distant ovate spots.” (Narrative of an Ex- 
pedition to explore the river Zaire, usually called the 
Congo in South Africa, in 1816, under the direction of 
Captain J. K. Tuckey, R. N. London, 1818, p. 410.) 
Head surrounded with Hight Arms without Feet. 
The suckers have soft margins. The sac is destitute of 
fin-like expansions, and is either simple or strengthened in 
the interior by two short corneous processes. The head is 
united with the sac behind, without the intervention of a 
neck. 
a. Arms all equal in Size. 
Genus Ocrorus.—Suckers arranged in a double row. 
The suckers are sessile. The oviduct is double. The 
margin of the anus is simple. The Sepia octopodia of Lin. 
is the type of the genus. 
2¥ 
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