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IV.—Contributions to the Palæontology of the Yorkshire Oolites.1

Published online by Cambridge University Press:  01 May 2009

Wilfrid. H. Hudleston
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Extract

In England the Great Oolite of Minchinhampton contains the greater number of species belonging to this peculiar group of Haliotidœ. Morris and Lycett (Great Oolite Mollusca, p. 80) give a full and interesting diagnosis of the genus, which has oniy one representative in the Corallian beds of Yorkshire. D'Orbigny figures half a dozen species of Troehotoma from the Corallian of France, and Buvignier gives three from the Coral Rag of the Meuse. None are quoted by Be Loriol from the Séquanien of Boulogne.

Type
Original Articles
Information
Geological Magazine , Volume 8 , Issue 3 , March 1881 , pp. 119 - 131
Copyright
Copyright © Cambridge University Press 1881

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References

page 119 note 2 I am indebted to Professor Morris for the following note with reference to the authorship of this genus:—“ Described by Deslongchamps in 1841, and first published in the Mem. Soe. Linn. Norm. vol. vii. 1842. Lycett sent the proposed name with a specimen to Sedgwick in 1841, but without any description. The first description by Lycett appears to be in the Annals and Magazine of Natural History for 1848, 2nd series, vol. ii. p. 253, and more fully in the Great Oolite Mollusca, 1850. It would seem therefore that Deslongchamps has the priority of publication. S. P. Woodward in his Manual assigns it to Lycett, although both authors suggested the name Trochotoma about the same time, 1841–42.”

page 122 note 1 It should be borne in mind that the Coralline Oolite of Scarborough Castle is lower geologically than the Coralline Oolite of Malton.

page 122 note 2 Sowerby's species is a fossil of the Inferior Oolite, originally described (M. C. t. 220, fig. 2) from Dundry. He gives two figures, but does not distinguish them by letter or numeral. The specimens are not in the type collection at the New Natural History Museum. Nevertheless, since a fossil similar to the right-hand figure is so common in the Inferior Oolite of Bradford Abbas and elsewhere, we cannot be in doubt as to the form of Sowerby's species. That author says that ' the granulated surface is the result of decussating furrows which vary in depth and number in different individuals.” I have examined a large series of English specimens from the Inferior Oolite, and find that Sowerby's P. granulata, though subject to great variety, has a much wider spiral, angle, is more umbilicated, and has a greater. variety of ornamentation. Nevertheless there are forms in the Inferior Oolite of Normandy classed by Deslongchamps as varieties of P. granulata (see Mem. Soc. Linn. Norm. vol. viii. pi. 16, fig. 6a), which lead up to the Cornbrash species, and also to the form now under consideration. See also a figure in Quenstedt's Der Jura, pi. 57. fig. 7, of a fossil from the Brauner Jura delta, p. 414. Still the elements of the Pleurotomaria in the Yorkshire Cornbrash, which must be regarded as very closely related to the shell now figured, are clearly not those of PL granulata, Sow., in any respect beyond the granulated character of the general sculpture. We have seen that Sowerby regarded the granulated surface of his species as the result of decussating furrows varying in depth and number; hence, when we bear in mind like wise the great differences in external appearance due to various conditions of mineralization, too much stress should not be laid upon mere granulation.

page 123 note 1 Both the figure and description by Sowerby indicate that this species should be bicarinated. Yet in the type collection at the New Natural History Museum are three specimens not figured (the figured specimen should be at Cambridge), which dearly come from the Trigonia-heAs of AVeymouth, and belong to its very close relative, PI. Münsteri, the more usual Oxfordian form.

page 129 note 1 There may be some doubt as to whether all the spines of Cidaris—for the test is hardly ever met with—really belong to C. Smithii, "Wright, but no spine which could fairly be referred to C. florigemma has been found.