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II.—Note on two Rark Forms of Actinocamax from the English Upper Chalk. G. C. Crick—Actinocamax from the English Chalk

Published online by Cambridge University Press:  01 May 2009

G. C. Ckick
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Extract

The present note relates to two specimens. One was obtained by Mr. G. E. Dibley, F.G.S., from the Micrazter cor-anguinum zone of the Chalk at Gravesend, and now forms part of the British Museum collection (register number C. 10576); the other is in the collection of Dr. H. P. Blackmore, F.G.S., of Salisbury (to whom I am indebted for the loan of the fossil), and was obtained from West Harnham, near Salisbury, at the base of the zone of Actinocamax quadratus. Being the more nearly perfect, the Salisbuiy specimen is described first.

Type
Original Articles
Information
Geological Magazine , Volume 4 , Issue 9 , September 1907 , pp. 389 - 395
Copyright
Copyright © Cambridge University Press 1907

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References

page 392 note 1 The term ‘alveolus’ is frequently somewhat loosely applied. The ‘alveolus’ is really the conical cavity at the proximal end of the guard of a typical Belemnite into which the phragmocone fits. Usually, however, in the genus Actinocamux the portion of the guard immediately in contact with the sides of the phragmocone was not calcified, and during fossilisation was destroyed ; when, therefore, a conical cavity is preserved in the genus its sides are not those of the ‘alveolus,’ but those of a cavity having a greater angle than the ‘alveolus.’

page 392 note 2 See figures of the alveolar end of various forms of Actinocamax in the Geol. Mag., 1904, p. 409.

page 494 note 1 Bull. Soc. geol. France, ser. in, torn, xix, Xo. 9 (Nov., 1891) pp 720 721 pi. xiv, fig. 5, and text-fig. 4.

page 494 note 2 Ibid., pp. 716–719, pi. xiv, figs. 1–3, and text-figs. 2, 3.

page 494 note 3 Proc. Geol. Assoc, vol. xvi, pt. 9 (August, 1900), p. 495.