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The Identification of Graptolites

Published online by Cambridge University Press:  01 May 2009

G. L. Elles
G. L. Elles
Affiliation:
University of Cambridge
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Extract

There are unfortunately few graptolites that have retained their original chitinous periderm;when these are preserved in rocks of suitable composition they may be isolated from the matrix, and having escaped distortion, may then be studied more or less in their original condition, and much of our knowledge concerning the structure shown by this group of fossils has, in recent years, been derived from such specimens;these, since they are preserved more or less in relief, differ greatly in appearance from the film-like fossils which are of far commoner occurrence, and which can rarely be taken at their face value, but require some degree of interpretation before identification is possible. Lapworth and Nicholson both recognized this, and it is much to be deplored that modern palaeontologists too often ignore this necessity for interpretation and take graptolites at their face value, with the result that specimens that are only views of well-known species are described as new species or varieties, and the literature of the subject is again being burdened with a number of names of no scientific value or significance.

Type
Articles
Information
Geological Magazine , Volume 81 , Issue 4 , August 1944 , pp. 145 - 158
Copyright
Copyright © Cambridge University Press 1944

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References

page 146 note 1 For the significance of the terms “dependent”, “declined”, etc., see Monograph of British Graptolites, p. 7, fig. 3.Google Scholar

page 146 note 2 I regard the disc-like structures often visible and enveloping the proximal region as probably functioning in this capacity.Google Scholar

page 146 note 3 Elles, G. L., Quart. Journ. Geol. Soc, liv, 1898, p. 501, fig. 2c.Google Scholar

page 147 note 1 Elles, and Wood, , Monograph of British Graptolites (Palaeont. Soc. London), pi. ii, fig. 4a.Google Scholar

page 147 note 2 Ibid., pi. ii, fig. 5a.

page 147 note 3 Elles, G. L., Summ. Progress Geoi. Survey for 1932, p. 100.Google Scholar

page 147 note 4 Elles, and Wood, , Monograph of British Graptolites, pi. ix, figs. Ac, Ad.Google Scholar

page 148 note 1 The denticle is the apparent corner or angle constituted in compressed forms by the meeting of the apparent profile of the apertural margin and the apparent profile of the free edge of the theca.Google Scholar

page 148 note 2 Elles, and Wood, , Monograph of British Graptolites, figs. 325–9.Google Scholar

page 150 note 1 Tornquist, S. L., Monograptidae of the Scanian Rastrites Beds. Lunds. Univ. Årsskr., xxxv, Afd. 2, No. 1, pi. iii, figs. 7–10.Google Scholar

page 150 note 2 Perner, J. Graptolites de Boheme, Pt. Ill (Sect. A), pi. x, figs. 18a, b, 22 (Jobiferus undulatus), and pi. x, figs. 19, 21 (lobiferus lapworthi).Google Scholar