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Studies in the Corallian Lamellibranch Fauna of Oxford, Berks, and Wilts1

Published online by Cambridge University Press:  01 May 2009

W. J. Arkell
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Extract

The greatest diameter of a Pecten is nearly always the height. It is easier to visualize the size of a shell from this measurement than from the length. Consequently in tabulating the dimensions of the species the height is first given in millimetres, followed by the length as a percentage of the height. Since in the vast majority of the ordinary species the shell is, except for the auricles of the right valve, subequilateral, no obliquity measurement is necessary as with the Limidae. Another redundant measurement in dealing with Jurassic Pectinidae is the inflation. This dimension is always such a small percentage of the height that accuracy of measurement without special apparatus is a matter of difficulty unless both valves happen to be joined, closed, and free from matrix. Even such differences as do exist can rarely be detected in allied species, such as might be liable to confusion in other respects.

Type
Original Articles
Information
Geological Magazine , Volume 63 , Issue 12 , December 1926 , pp. 534 - 555
Copyright
Copyright © Cambridge University Press 1926

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Footnotes

1

Continued from Vol. LXIII, p. 210.

References

page 536 note 1 The classification here adopted is that of Philippi, Beiträge zur Morphologie und Phylogenie der Lamellibranchier, II, Zur Stammesgeschichte der Pectiniden; Zeitschrift der Deutschen Geol. Gesellschaft, lii, 1900, pp.64–117. Sub-generic descriptions principally adapted from those of Verrill,; A Study of the Family Pectinidae, with a Revision of the Genera and Sub-genera; Trans. Connecticut Academy, x, 1899, pp. 41–95.

page 539 note 1 Compare the right valves figured by Goldfuss, Petrefacta, pl. xc, 10, and Sowerby, Min. Conch., vol. vi, pl. Dxliii, 2.