A Monograph of the Eocene Cephalopoda and Univalves of England, Volume 1, Parts 1-4

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Palĉontographical Society, 1849 - Cephalopoda, Fossil - 361 pages
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Page 16 - ... formation occurs Clymenia, which forms a link with the Goniatite of the mountain limestone, a fossil approximating, if not fully belonging to the Ammonite family. The distinctions are chiefly in the form of the septa or walls which divide the chambers of the shells. A living palaeontologist says — " As we ascend in the Palaeozoic series, we find that various of the primitive genera and species disappear, and are succeeded by other forms, distinct from, but closely allied to them; which, in...
Page 42 - De Haan. Gen. desc. Animal; body oblong, posteriorly rounded, and terminating in a slender membranaceous tube; head above, with an ambulatory disc ; arms, nineteen (?) on each side ;* labial tentaculiferous appendages, four, arranged round the mouth ; tentacula of three kinds, viz. ophthalmic, lamellose, two on each side ; brachial, annulose, twenty on each side; labial, annulose, twenty-four on each side; the whole body contained in the last chamber of a large multilocular shell, and affixed by...
Page 7 - Zoologie,' and in Madame Power's ' Observations on the Poulpe of the Argonaut,' translations of which are published in the 'Mag. Nat. Hist.,' new series, vols. iii and iv. The observations of Mr. Adams, published in the ' Zoology of the Voyage of the Samarang,' tend to prove that the shell is constructed by the female Argonaut as a nest for receiving her eggs, and protecting them from injury, resembling in some measure the rudimental capsules secreted by many marine Gastropods for the preservation...
Page 67 - H. labyrinthica. Shell conic, dark reddish-brown, body lighter; -whorls five or six, with conspicuous, elevated, equidistant, obtuse lines across, forming grooves between them; apex obtuse; lip reflected, rounded; pillar lip with a large, lamelliform, elongated tooth, which appears to revolve within the shell parallel to the suture, a smaller raised line revolves nearer to the base within the shell, but becomes obsolete before it arrives at the pillar lip; umbilicus rather large. Breadth one tenth...
Page 13 - I am much disposed to believe, that in every distinct formation of shell-substance there is a single layer of membrane; and I am further of opinion that this membrane was at one time a constituent part of the mantle of the mollusc.
Page 83 - ... rudimentary lateral jaws, a large central spiral body, and a simple-edged mantle, covered by an external ovate, thin, dextral, transparent spiralshell with an ovate mouth, having a single oblique plait on the middle of the column running into the axis. " Limnsea has a small central tooth, as it were squeezed up between two very large lateral ones, each primary lateral having a very large apex internally, with a small external one, while at the edge they have altered to one thick prolonged apex...
Page 13 - ... this state they somewhat resemble the incipient form of the prismatic cellular substance. These cells may be occasionally seen in sections of the shell itself; and they will be often found in very different degrees of development even in the corresponding layers of two shells of the same species. Coupling the appearances which I have myself observed with the observations of Mr. Bowerbank, on the formation of shell, and keeping in view the general doctrines of cell-action, which I have elsewhere...
Page 338 - ... between existing groups and species ; while the careful study of living forms has brought into prominence the variations dependent on food, climate, habitat, and other conditions, and shown that many species, long supposed to be absolutely distinct, are so closely linked together by intermediate forms that it is difficult to draw a satisfactory line between them. The principles of classification point also in the same direction, and are based more and more on the theory of descent. Biologists...
Page 341 - The following Fluviatile shells from the Lower Tertiaries of England may, I think, be separated into genera or sectional divisions, as indicated by the operculum ; and had I been able to continue this work, it was my intention to have done this. 1. PITHARELLA, Edwards, 1860. " Shell subcylindrical ; spire obtuse, more or less produced ; aperture oval-oblong, rounded in front, narrowed behind ; columella straight or very slightly twisted, arched anteriorly ; outer lip simple, acute ; inner lip thickened.

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