Published online by Cambridge University Press: 17 January 2013
Concerning the affinities and systematic position of this very remarkable Devonian fish, there has hitherto prevailed very great uncertainty. The two original specimens, discovered by Mr C. W. Peach, in the Old Red Sandstone of John O’Groat’s, Caithness, and described by Sir Philip Egerton, left us in complete ignorance as to the osteology of the head and the dentition, while the evidence they afforded as to the structure of the pectoral fins was by no means so clear as might have been wished for. To quote from Sir Philip's description:—“ The bones of the head, with the exception of a small fragment of the operculum, are wanting, but the impressions left upon the matrix show that they were sculptured in rather a bold pattern, not unlike the ornament on some of the cranial bones of some of the Holoptychii, and consequently differing in this respect from the corresponding parts in Dipterus. The pectoral fins are very indistinctly seen. They appear to have had a short obtuse lobe forming the base, and extending therefrom a set of numerous fin-rays more elongated than those forming the pectoral fin in Dipterus.” To Dipterus, however, in Sir Philip Egerton's opinion, its affinities pointed, as far as could be gathered from the structure of the body as displayed in the specimens, his description concluding as follows:—“ The absence of all evidence as to the dental apparatus of Tristichopterus is much to be regretted. On other points the affinities between this genus and Dipterus are so striking that they cannot be classified in separate families. Accordingly he assigned to Tristichopterus a place along with Dipterus in the family of “Cœlacanthi,” the term being used in its former extended sense, not as now restricted to the peculiar genera Cœlacanthus, Undina, Holophagus, and Macropoma.
page 383 note * Dec. Geol. Survey, x. 1861, pp. 51–55, pl. v.Google Scholar
page 383 note † Loc. cit. p. 55.
page 383 note ‡ Dec. Geol. Survey, x. 1861, p. 40.Google Scholar
page 384 note * Description of Ceratodus, Phil. Trans. 1871.
page 384 note † These specimens are now in the Museum of Science and Art, Edinburgh.
page 386 note * Dec. Geol. Survey, x. p. 2.
page 386 note † Shoulder Girdle and Sternum, p. 19.
page 386 note ‡ Ueber die Saurodipterinen, &c., des Devonischen Systems, St Petersburg, 1860, p. 11-12.
page 389 note * Since the above lines have been in type, the Museum has acquired from Mr Peach an additional and nearly perfect specimen of Tristichopterus, in which, near the front of the head, the base of one of the large teeth is seen broken, or cut, across in transverse section. The transverse section of this tooth is ⅛ inch in diameter, and displays a structure absolutely identical with that described above.
page 391 note * The tail of Polypterus is not, however, absolutely diphycereal, though conforming more to that type than to any other.
page 394 note * Ueber die Begrenzung und Eintheilung der Ganoiden; Palæontographica, Bd. xxii., Erste Lieferung, 1873, p. 47.
page 394 note † Op. cit. pp. 55-61.
page 395 note * Dec. Geol. Survey, x. p. 23.
page 395 note † British Palæozoic Fossils, pp. 596-597, Plate 2, C, figs. 2, 3.
page 395 note ‡ Qu. Journ. Geol. Soc. xvi. (1860) p. 126.Google Scholar
page 395 note § Dec. Geol. Survey, x. p. 23.
page 395 note ║ Dec. Geol. Survey, x. p. 54, note.