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III. On Acrodus Anningiæ, Agass.; with Remarks upon the Affinities of the Genera Acrodus and Hybodus

Published online by Cambridge University Press:  01 May 2009

E. C. H. Day
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Extract

Few amongst the Fish-remains preserved to us in the Secondary roacks are more commonly met with than those of Sharks of the genera Acrodus and Hybodus; yet, not-withstanding the frequency of their occurrence, we have but little exat knowledge of the from and affinities of the fish to which these remains beleonged. Their cartilaginous skeletons have, expecting a few fragments, altogether pershied; and it is quite impossible to guess at their outlines, undefined as these were either by scales or hard plates. Nay, more, the remains that are known of these extinct forms present such great differences from the corresponding structures of living fish, that, although a relationship to a single existing genus has long been indicated, the degree of that affinity is still very uncertain.

Type
Original Articles
Information
Geological Magazine , Volume 1 , Issue 2 , August 1864 , pp. 57 - 65
Copyright
Copyright © Cambridge University Press 1864

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References

page 57 note * , Agassiz, 1838.Google Scholar

page 57 note † Ibid. 1837.

page 57 note ‡ The volume containing those that form the subject of the present paper was published 1833–43.

page 57 note § , Agassiz, ‘Poissons Fossiles’, vol. iii. p. 139.Google Scholar

page 57 note ‖ Ibid. p. 206.

page 58 note * , Agassiz, ‘Poissons Fossiles’, vol. iii. p. 159.Google Scholar

page 58 note † Ibid. p. 178, 179.

page 58 note ‡ Ibid. p. 139, and again at p. 207, where, after speaking of the internal structure of Hybodont teeth, he goes on to say: ‘Cette structure des dents s'oppose comme on le voit, au rapprochement que M. Owen' (in his ‘Odontography’) ‘a tenté entre les dents des Hybodontes et celles des Cestractiontes, en effeet les couronnes plates les qui distinguent les dents des Cestractiontes et qui font des instruments propres à broyer la nourriture n' ont rien de commun avec les couronnes élevées et coniques des Hybodontes, qui quoique obtus dans quelques, espèces étaient èvidemment destinées á saisir et á retenir une profie.’ It must be remembered, however, that, when Agassiz made this generalization, he had classed as a Hybodont tooth the cephalic spine of Hybodus. Ibid. p. 208.

page 58 note § Ibid. pp. 141 and 182.

page 58 note ¶ Ibid. pp. 140.

page 59 note * One of these is displaced to the outside of the third row.

page 59 note † The single detached tooth outside these appears to belong to the central row.

page 59 note ‡ The sixth tooth of this row is scarcely visible.

page 60 note * I believe this species to be identical with H. pyramidalis of Agassiz.

page 60 note † Some of the teeth answer likewise to his figure of A. gibberulus. Agassiz appears to have been acquainted with the latter teeth before he named the fragment of A. Anningiæ, which I cannot find that he has anywhere described. As the two species are, however, figured side by side, and were consequently, I presume, published together, I feel justified in taking my choice of the two names; and I prefer A. Anningiæ, as belonging to the best characterized specimen, and as preserving the name of one to whom Palæontologists are deeply indebted.

page 61 note * I take the opportunity of acknowledging the courtesy of G. E. Waterhouse, Esq., and of Dr. Günther, of the British Museum, as also of Professor Huxley, of the Museum of Practical Geology, in affording me every facility for the examination of specimens under their care, and in drawing my attention to several which were of much interest, as elucidating my subject, and which otherwise I might not have noticed.

page 61 note † In Lord Enniskillen's magnificent collection, at Florence Court, there is a portion of a Saurian containing between the ribs two spines and many large teeth of Acrodus nobilis; and in the Museum of Practical Geology there is a smaller fragment of a Saurian ‘interior’ which displays teeth, two cephalic spines, and part of a dorsal, of Hybodus reticulatus, associated with teeth and part of a dorsal spine of Acrodus latus (?). These specimens are very suggestive of the destructive capabilities of the Ichthyosauri.

page 62 note * Charlesworth, Mag. of Nat. Hist. 2nd ser. 1839, p. 245. Owen, ‘Odontography,’ as quoted above by Agassiz.Google Scholar Ibid. ‘Palæontology,’ p. 108. Mackie, the Geologist, 1863, p. 243. On the other hand, Pictet, in his ‘Paléontologie,’ 1853–1857, vol. ii. pp. 254 and 260, retains the error of classifying the two in different families; as is likewise done in Morris's ‘Catalogue of British Fossils,’ on the authority of Professor Owen's ‘Lectures on Comparative Anatomy,’ vol. ii. p. 47. A less comprehensible oversight occurs in Owen's ‘Palaeontology,’ where a side view of the head of Myliobates is apparently copied from Agassiz and referred to in the text as that of Cestracion Philippi, p. 106.

page 63 note * The most marked expection to this generalization is Hybodus basanus, described by Sir Egerton, P., Quart, Jour. Geol. Soc., vol.i. p. 197.Google Scholar

page 64 note * Is not the spine which Agassiz called Leptacanthus, and classed with the Hybodonts, that of a Chimæroid ? At least, it has only occurred in strata in which Chimæroid jaws have likewise been met with.

page 64 note † Ag. ‘Pois. Fos.’ vol. iii. p. 336.Google Scholar

page 64 note ‡ Mag. Nat. Hist. 2nd ser. vol. iii. p. 245.Google Scholar

page 64 note § See note by Miss Anning, Ibid. p. 605, and which statement I myself have been frequently able to verify.

page 64 note ‖ The name given by Agassiz to these fossils, which he considered to be the teeth of a Hybodont.

page 65 note * The very rough shagreen with which Hybodus was covered is not so well exemplified by that of Cestracion as by that of Centrina (another genus of spined Sharks), in which the coarse, tooth-like asperities very much resemble those of the fossil.

page 65 note † Dissected and drawn (from a specimen preserved in spirits) by Mr. Henry Woodward.