Identifier: quarterlyjourna101854geol (find matches)
Title: The Quarterly journal of the Geological Society of London
Year: 1845 (1840s)
Authors: Geological Society of London
Subjects: Geology
Publisher: London (etc.)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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trans-verse articulations and fimbriated extremities. They converge at thebase, and appear to have been supported by a process or processesgiven off from the upper surface of the vertebral column. In thelower lobe I count eleven similar rays, apparently similarly divergentfrom the under surface of the column. The central portion of thefin is filled up by five or six weak rays, which subdivide at a shortdistance from their bases. The scales project slightly over each lobeof the tail, the extreme ones being in the centre of the upper lobe,and not on the upper margin, as in a true heterocerque tail. The dermal investment is of great strength and solidity. Thescales are numerous, and provided with a thick coat of ganoine. Theyare also firmly interlocked and strengthened by an unusually largeoverlap. The exposed parts, in consequence of the latter provision,are high and narrow, except in the vicinity of the tail, where theyare more lozenge-shaped. The surface of the enamel is very uneven,
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1854.) EGERTON FOSSIL FISH FROM THE DECCAN. 371 and the free edges of the scales are rudely and irregularly notched.The mode of articulation is not very well seen, but it appears to havebeen by means of a broad central rib, somewhat resembling thisarrangement in the genus Aspidorhynchus, and not by means of amarginal rib, as in the Pycnodonts. There are fourteen rows in thedorso-ventral series, and thirty-four in the longitudinal direction.The lateral duct pierces a row of broad scales extending from theupper margin of the opercular apparatus to the centre of the tail. The characters described in the foregoing details show Diptero-notus to be a member of the Lepidoid family of Ganoids. Its posi-tion in that family cannot be assigned with any degree of certainty;but it may at all events be provisionally arranged near the genusJEurynotus. I may add that, having forwarded to Professor Agassiz a drawingof the tail, together with my reasons for considering it a homocerqueform, he has kindl

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