Notes on the Carboniferous Cephalopoda

Downloaded from http://pygs.lyellcollection.org/ by guest on October 1, 2021 257 some two miles inland, at an elevation of about 200 feet above the sea-level; and more recently have had a specimen given to me, said to have been found in Cornwall, but I am somewhat dubious about the accuracy of this locality. I am under the impression that Yermiculite Granite will be found in Yorkshire, especially in the northern division of the West Riding; and I trust our geological friends will carefully examine any granite boulders they may meet with in their excursions. It is only when the Granite is decomposed that the mineral can be properly separated from it; but even in situ, by careful observation, there will be no difficulty in detecting it. That these Granite boulders have travelled a long distance I am fully persuaded, and my belief is they have been transported to our shores in floating ice, very probably from Labrador. NOTES ON CARBONIFEROUS CEPHALOPODA. PART I. RECENT CEPHALOPODA. BY WILLIAM CASH, F.G.S. (PLATE XI.) THE true method of reasoning on natural objects and phenomena, is from that which is well known to that which is unknown; hence it follows, that a sound knowledge of the structure and relations of Fossil Animals can only be acquired by a careful study of the structure and relations of their living analogues. These and similar considerations have resulted in prefacing the proposed " Notes on Carboniferous Cepha• lopoda," with the following remarks on the structure, habits, distribution, and classification of their living repre• sentatives. The class Cephalopoda includes the most-highly organised members of the great Molluscan sub-kingdom. Its best known living types are the Argonaut, or Paper Nautilus, the Cuttle Fish, the Squid, and the Pearly Nautilus; whilst its extinct types include the Ammonite and the Belemnite, Fossils Downloaded from http://pygs.lyellcollection.org/ by guest on October 1, 2021 258 familiar to visitors at Lyme Regis and Whitby, who may see them offered there for sale in the shop-windows of the dealers, or may collect them for themselves from the Liassic strata, which are exposed in the cliffs and along the coast at those watering places. The Cephalopoda have always been objects of great in• terest to the Naturalist. So long ago as the reign of Alexander the Great, Aristotle, the father of Natural History, aided by the munificent liberality of his royal patron, wrote his remarkable " History of Animals," and with wonderful dis• crimination pointed out the difference between the naked forms (fxaXaKia) and the Nautilus, a true shell-bearer; and though more than 2,000 years have passed since then, it is surprising how marvellously little alteration is required to adapt his descriptions, so far as they go, to the results of modem research. It is recorded of the great French Com• parative Anatomist, Baron Cuvier, that whilst a young and ardent though comparatively unknown student of Zoology, he collected the Cuttle Fishes cast up on the sea shore, near his home in Normandy, dissected them and made drawings of them with their own ink, and thus laid the foundations of that brilliant reputation which he subsequently so justly won. Nearly half a century ago, Mr. George Bennett had the good fortune to capture, in Marekini Bay, at the island of Erro- mango, in the New Hebrides, a Pearly Nautilus (N. pom- pilius, Linne); this specimen was presented to the Eoyal College of Surgeons, London, and formed the subject of a valuable memoir, by Professor Owen.* The researches of such distinguished Naturalists as Van Beneden, Carus, Che'ron, Clarke, Cuvier, D'Orbigny, Eschricht, Ferrusac, Grant, Gren- acher, Hancock, Harting, Hensen, Yan der Hoeven, Huxley, Keferstein, King, Kolliker, Krohn, Lankester, Macdonald, Downloaded from http://pygs.lyellcollection.org/ by guest on October 1, 2021 259 Milne Edwards, Owen, Proseh, Rang, Ratlike, Risso, Steen- strup, Trinchese, Valenciennes, Verany, and Vrolik, some still living and working at the Cephalopoda, others speaking to us through their already accomplished work, have thrown a flood of light on the subject, and prove that the interest in this class of invertebrates has been handed down from one generation to another, and still survives ; nor must we forget that the recently returned, and now celebrated "Challenger Expedition " has furnished material which promises to add to our knowledge of the Cephalopoda, for the numerous marine treasures brought to England include at least one perfect specimen of the Pearly Nautilus, which was captured between New Zealand and the Fijis, in a depth of 300 fathoms,* and it is very gratifying to learn that this and the other Cepha- lopods collected have been placed in the hands of a distin• guished English professor for examination and description. STRUCTURE. The name Cephalopoda (Greek, Ke(pa\n, head j 7rou?, foot) has reference to the peculiar arrangement of the lobes (brachia) of the foot, in a circle around the head of the animal; this feature alone serves to distinguish the members of the group from all other molluscs whatsoever; whilst their highly developed nervous system and complex sensory organs at once declare their great superiority physiologically, and place them at the head of their sub-kingdom. General Form and Relations of the External Parts. Figs. 1 and 2 are sketches of a Cephalopod,f showing the relation of the arms to the head just mentioned, a relation which is constant in all the genera; and also illustrating the following common characteristics:— * " Log Letters of the Challenger, by Lord George Campbell." London, 1877. f From a specimen of Ommatostrepb.es todarus, Delle CMaje, preserved in spirits, and collected in the Irish Sea, 1875. Downloaded from http://pygs.lyellcollection.org/ by guest on October 1, 2021 260 The presence of a muscular mantle (M), enveloping a cylindrical or pouch-shaped body, to which anteriorly is attached a well-developed head (H), furnished with a pair of complex eyes (E), the lobes (brachia) of the so-called foot (AAA) are arranged in a circle around the mouth, which latter organ is armed with a pair of horny, bird-like mandibles (B), which work vertically. In the ventral region a fold of the mantle is prolonged into a funnel or siphon (r.)* GENERAL FORM AND RELATIONS OF THE INTERNAL PARTS. Fig. 3 is a diagram of the internal anatomy of a Cuttle Fish. The buccal mass (A), and the horny mandibles (B), along with the fleshy tongue or odontophore, with its siliceous radula, crown the long oesophagus or gullet; it is into this latter organ that the salivary glands (D) pour their secretion. The stomach (E) is connected anteriorly with the alimentary canal, and posteriorly with the plyloric ccecum (F), the liver (i) is connected with this organ by its hepatic ducts, the pyloris is continued to the intestine (G), which, bending upon itself, has its flexure neural, that is towards the nerve masses, and away from the heart (N) ; the intestine opens by the anus (H) into the mid-ventral region. Close by the orifice of the anus is that of the ink-bag (K), an organ, however, which is only found in the Dibranchiates. The position of the generative organs is indicated by the letter (o), and that of the plume like gills on the one side, by the letter (M). * For description of the general anatomy of the Cephalopoda, see " The Anatomy of Invertebrated Animals," T. H. Huxley, Lon., 1877; and " Forms of Animal Life," by George Eolleston, Oxford, 1870. For classification, &c, see " Manuel de Conchyliologie," Tome 1, J. Chenu, Paris, 1859; "Mollusques Vivants et Fossiles, Gephalopodes," A. D'Orbigny, Paris, 1855, and " Manual of the Mollusca," with appendix by Ralph Tate, S. P. Woodward, Lon., 1871. For description of Species, see "A Description of British Mollusca and then- Shells," E. Forbes and S. Hanley, Yol. iv., Lon., 1853. " British Oonchology," by J. G. Jeffreys, Vol. v., Lon., 1859. " Conchologica Iconica," " Loyell Reeve, Mono• graphs on Nautilus and Argonauta," Lon., 1861. " Mollusques Meditn. Gephalo• podes," J. B. Verany, Genoa, 1851; and " Histoire Naturelle des Mollusques; Monographic Cephalopodes," Ferrusac et D'Orbigny, Paris, 1834-5. Downloaded from http://pygs.lyellcollection.org/ by guest on October 1, 2021 261 Fig, 4 is taken from a dissection of the nervous system of Eledone cirrosa * Lamarck. The three principal pairs of nerve ganglia, namely, the cerebral, pedal, and parieto splanchnic, occur, as in the rest of the true Mollusca, but, being aggregated together, their connecting threads (com• missures) are not easily made out. In Fig. 4 are displayed the nerves of the arms (A A A), &c.; the auditory nerves (B) ; the nerves of the funnel (c); the accessory nerve of the mouth (D) ; the pallial nerves (F) terminating in the singular bird-foot-shaped ganglia; the branch of the visceral nerve to the muscles of the body (G) ; the ganglia of the branchial hearts (H) ; and the branchial ganglia (i). The nerves of the eye (optic) are largely developed. The Cephalopoda are divided into two orders: the Di- brcmchiata furnished with two gills, and the Tetrabranchiata having four gills; the JDibranchiata are divided into two groups: the Octopoda, including Cuttle Fish, with eight arms only, and the Decapoda, provided with eight brachia and two tentacles—ten arms. Having briefly enumerated the salient structural char• acters common to the class, we proceed to note some of the variations which occur in the lesser groups :— The Mantle.—This is the external skin which protects the viscera; in the naked forms it is usually tolerably thick and tough, but in the shell-bearing Nautilus, it is soft and membranous.

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