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III.—On some new Uniserial Cretaceous Cheilostome Polyzoa

Published online by Cambridge University Press:  01 May 2009

W. D. Lang
W. D. Lang
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Published by permission of the Trustees of the British Museum
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Extract

In 1890 Vine described Membranipora gaultina a uniserial Cheilostome from the Cambridge Gault. A peculiarity of this species was ‘a puckering’ or ‘folding-in of the wall below the area’ shown by Vine in his figure of the type-specimen. Unfortunately this specimen cannot be found; but a well-preserved paratype specimen (from the same horizon and locality) exhibits the same structure and shows that this is due to the collapse of the extra-terminal front wall along a median line proximal to the aperture. Other zoœcia of the same specimen show the extra-terminal front wall entire and a thin median seam—or rhamma—running proximally from the aperture. The rhamma appears in some instances as a ridge and in others as a depression; in some zoœcia it is not apparent; and when visible is extremely fine. In many cases the front wall is broken along it (as in Vine's figure) and thus the rhamma probably indicates a line of weakness. It is suggested that the rhamma is a ridge bounded by two furrows and that the front wall is thicker at the ridge and thinner in the furrows. The rhamma, then, would easily be broken off, and in such specimens a depression would appear in its place; and a thin groove on each side would constitute a general line of weakness which would account for the frequent breaking down of the front wall.

Type
Original Articles
Information
Geological Magazine , Volume 2 , Issue 11 , November 1915 , pp. 496 - 504
Copyright
Copyright © Cambridge University Press 1915

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References

page 496 note 1 Vide Walcott on Olenellus gilberti, in Smiths. Misc. Coll., vol. liii, p. 327, 1910. The discovery of the presence of a visual area in Olenellus gilberti is against Wood's suggestion (op. cit., p. 232) that the eye-like lobe of Olenellus “is really of the nature of a pleura”.

page 496 note 2 Neuadia, Burlingia, Marella, Nathorstia, are all more primitive than Conocoryphe, and yet they all possess well-formed eyes. Again, secondary loss of eyes is now definitely established in some families, e.g. Trinucleidæ.

page 496 note 3 Q.J.G.S., 1895, p. 359.Google Scholar

page 496 note 4 \tau \acomicron \ \llrho \acalpha \mu \mu \alpha, ‘a seam.’

page 496 note 5 Vine, , 1890, Quart. Journ. Geol. Soc., vol. xlvi, pp. 484, 461.Google Scholar

page 497 note 1 Vine, , 1892, Proc. Yorks. Geol. Poly. Soc., new series, vol. xii, part 2, pl. vi, fig. 15.Google Scholar

page 497 note 2 Vine, 1890, loc. cit.

page 497 note 3 Vine, 1890, op. cit., p. 461.

page 497 note 4 Mantell, , 1844, “Medals of Creation,” p. 285, pl. lxiv, figs. 3, 10, 10b.Google Scholar

page 497 note 5 For these terms, see Lang, , 1914, Geol. Mag., Dec. VI, Vol. I, p. 6.Google Scholar

page 499 note 1 In memory of Mary de Valence, Countess of Pembroke, foundress of Pembroke College, Cambridge.

page 500 note 1 Carixa, an old name of Charmouth (the type locality ; see Roberts, 1823, “The history of Lyme Regis, Dorset,” p. 220), probably = ‘Char, isca’ (altered to ‘ixa’ as in Exe, Axe, &c.), i.e. “Char river”. I have therefore altered the spelling to Charixa that this generic name may better recall the locality.

page 501 note 1 From Black Ven, the cliff from which the type-specimen came.

page 501 note 2 d'Orbigny, , 1849, Revue et Magasin de Zoologie, 2nd series, vol. i, p. 499.Google Scholar

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page 501 note 5 Edwards, , 1838, Annales des Sciences Naturelles, series ii, Zoologie, vol. ix, pp. 208, 238, pl. xvi, fig. 4 ; genotype C. Michelinii.Google Scholar

page 501 note 6 i.e. with a distal bud and one lateral bud.

page 502 note 1 \tau \acomicron \ \mu \upsilon \sigma \tau \rho \aciota \omicron \nu, ‘a spoon’; the normal zoœcia resemble the bowl of a spoon.

page 502 note 2 Reuss, , 1846, Verstein. bohm. kreideform ; part 2, pp. 67–8.Google Scholar

page 502 note 3 Lang, 1914, op. cit., p. 443.

page 502 note 4 Edwards in Lamarck, 1836, “Hist. Nat. Animaux sans Vertèbres,” 2nd edition, vol. ii, p. 230.Google Scholar

page 502 note 5 \delta \iota- prefix meaning ‘two’ and \lleta \ \sigma\tau\aceta\lambda\eta ‘a post’.

page 503 note 1 bi- prefix meaning ‘two’ and pila ‘a pillar’.

page 503 note 2 Lang, , 1914, Geol. Mag., Dec. VI, Vol. I, pp. 5 and 436.CrossRefGoogle Scholar