SECTION A. Octopoda.
Fain. 1. Argonautidie.
Genus, Argonauts, argonaut or paper sailor, recent, 4 sp. ; fossil, 1 sp. ; syn. Ocythoe nautilus.
Fara. 2. Octopodidn.
Genera, Octopus, recent, 46 sp., syn. Cistopus.
Sub-genus, Tremoctopus, recent, 2 sp.
Pinnoctopus, finned octopus, recent, 1 sp.
Eledone, recent, 2 sp.
Cirroteuthis, recent, 1 sp. C. Miilleri. Philonexis, recent, 6 sp.
Professor Owen divides the octopods into two groups or families, the Testacea and the Nuda. The Testacea consist of the genera Argonauta and Bellerophon. Of Argonauta, several species occur in the seas on the south and cast of Asia, viz. A. argo, cornu, cymbium, gondola, hians, thaustrum, tuberculate, and vitrea. A. argo has been from the earliest periods an object of interest to zoologists, in consequence of the accounts of its sailor-like habits handed down to us from Aristotle, Pliny, /Elia'', Oppian, and others ; and iu consequence of the difference of opinion enter tained with regard to the inhabitant of the shell by naturalists. In 1836, Madame Jeannette Power laid before the Academy at Catania her Osservazione Fisiche sopra it Polpo de l'Argo nauta Argo, in which, after a lone. and careful course of inquiry, she ascertained that it con structs its own shell. The argonaut is furnished with eight arms, having on each two rows of suckers ; the first two arms are more robust than the others, and should be so because they serve as masts to support the sails, which, spread out, act before the wind as such. At the base they have on the inferior sides the double row of suckers, like the other six ; but from the inferior row, at about an inch from the base in adults, a rather furrowed me rnbrane begins to developo itself, which extends as far as the tip of the arm, and, holding it bent, it can no longer execute the office of a rowing arm, but is employed by the animal as a sail. These sails are so large that, when turned backwards and pressed against the shell, they can entirely cover and protect it. The true office of these sails is that of keeping themselves applied to the shell at all times, in reserve for the moment when the animal, coming to the surface of the water, removes them, and, spreading them, raises them as sails. In fact, the series of suckers of the sail-arms when the membrane of the sails is wrapped about the shell, is placed exactly over the keel of it, in such a manner that each sucker corresponds to each point in which the ribs of the shell terminate, until they reach the two margins of the spiral. Captain Philip Parker King, R.N., during his passage from Santos to St. Catherine's, in lat. 28° S., caught a dolphin (Coryphoia), the maw of which was found filled with shells of Argonauta tuberculosa (Arufa of Owen), and all containing the Octopus ocythoe that has been always found as its inhabitant. Most of the specimens were crushed by the narrow passage into the stomach, but the smaller ones were quite perfect, and to some of them was attached a nidus of eggs, which was deposited between the animal and the spire. The shells varied in size from two
thirds of an inch to two and a half inches in length ; each contained an octopus, the bulk and shape of which were so completely adapted to that of the shell, that it seemed as if the shell increased with the animal's growth. In no speci men did there appear to be any connection between the animal and the shell. Several species are already known as inhabitants of the seas of warm latitudes, both littoral and pelagic.
Eledone, Aristotle, Leach. Arms provided with a single series of sessile acetabula.
E. ventricosa, Octopus ventricosus, Grant. Body short, round ; the eight arms connected at their base by a membrane.
Octopus, Lan, Leach. Its arms are provided with a double alternate series of sessile acetabula.
O. vulgaris, Sepia octopodia, Linn.; Sepia octopus, Gmel. Body short and ovid, the eight arms connected at their base by a wide membrane. The octopus is eaten by the Chinese and Japanese.
Madame Power, writing on the habits of the poulpe or cuttle, mentions that into one of her aquaria she had put a living Pinna nobilis adher ing a fragment of rock ; this aquarium also contained an Octopus vulgaris and some living testaceous znollusca. One day she saw that the poulpe was holding a fragment of rock in one of its arms, • and watching the pinna, which was opening its valves. As soon as they were per fectly open, the poulpe placed the stone between the valves, preventing the pinna from closing them again, when the octopus set about devour ing the mollusc. The next day she saw the poulpe crush some Tellinm, then search about amongst other shells, and finally stretch itself close to a Triton nodiferum. The triton extended half the body from its shell, no doubt to seek its food, when the poulpe sprang upon it, and surrounded it with his arms ; the mollusc retired precipitately into its shell, and in closing this, with its oper culum pinched the point of one of the arms of the poulpe, which, by struggling, at last left the tip of its arm in the shell of the triton. The voracity of the poulpe was such, that, notwithstand ing the abundance of nourishment with which she furnished it, she was compelled to remove it from the aquarium, or 3t would have devoured all the mollusca. So great is its voracity, that it even attacks man, tears away his flesh, and eats it. In the port of Messina they occur in great num bers, and of large size. One Octopus Chinensis, measured by Adams, was 6 feet from tip to tip of the arees.—Adeenture and Beagle Voyages; Madame Jeannette Power, Mag. Nat. Hist. ; Eng. Cyc. ; Woodward's Shells; Indian Field; A. Adams' Tr. in Japan.