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I.—On the Structure of the Frontal Spine and the Rostrolabial Cartilages of Squaloraja and Chimæra

Published online by Cambridge University Press:  01 May 2009

Otto M. Reis
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Extract

The remarkable frontal spine of Squaloraja has always been described as a dermal structure by those who have referred to it, and has been classed with the shagreen-granules and dentition. After the systematic position of the genus had been determined, its frontal spine was rightly recognized as identical with the spine-like frontal process in Chimæra and fossil Holocephala, with which it was formerly compared by W. Davies and A. S. Woodward. Both these processes were regarded as dermal structures by von Zittel, Jaekel, and A. S. Woodward, and treated as true ichthyodorulites, i.e. as if consisting of dentine or vasodentine. In 1890 the present writer briefly pointed out that the frontal spine of the Jurassic Chimæroid, Ischyodus avita, consisted of extremely calcified fibro-cartilage, resembling that of the so-called “claspers” of all male Elasmobranchs. The microscopical structure of these parts differs conspicuously from that of the calcified granules in the common (hyaline) cartilage of the internal skeleton, and its ontogenetic development is different.

Type
Original Articles
Information
Geological Magazine , Volume 2 , Issue 9 , September 1895 , pp. 385 - 391
Copyright
Copyright © Cambridge University Press 1895

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References

page 385 note 1 Woodward, A. S., Cat. Foss. Fishes Brit. Mus., pt. ii, p. 40 (1891).Google Scholar

page 385 note 2 Davies, W., Geol. Mag., Vol. IX, p. 145, pl. iv (1872).CrossRefGoogle Scholar

page 385 note 3 Woodward, A. S., Proc. Zool. Soc. 1886, p. 527.Google Scholar

page 385 note 4 von Zittel, K. A., Handb. Palæont., vol. iii, p. 95.Google Scholar

page 385 note 5 Jaekel, O., Sitzungsb. Gesell. naturf. Freunde, Berlin, 1890, pp. 120, 127.Google Scholar

page 385 note 6 Woodward, A. S., op. cit. 1891, p. 40.Google Scholar

page 385 note 7 O. Reis, Geognostische Jahreshefte, 1890, p. 8.

page 385 note 8 O. Jaekel, Die Selachier vom Monte Bolca (Berlin, 1894).

page 385 note 9 “Es besteht aus einer hohlen Kalkröhre deren peripherische Teile aus zusammengeschmolzenen Kügelchen bestehen, worauf vereinzelt sternförmige Dentin-schuppen sitzen” (op. cit., p. 65).

page 386 note 1 Vetter, B., Jena Zeitschr. f. Naturw., vol. xii, p. 441.Google Scholar

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page 388 note 1 Jaekel, O., Sitzungsb. Gesell. naturf. Freunde, Berlin, 1890, pp. 119–131.Google Scholar

page 388 note 2 See Catal. Foss. Fishes Brit. Mus., pt. i, pl. iii, fig. 4.Google Scholar

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page 389 note 1 Gegenbaur, C., Untersuch. vergl. Anat. Wirb., pt. iii, p. 206.Google Scholar