Before the type of a new and strange form called _Pterichthys_, had been determined by this learned palæontologist, collectors were everywhere puzzled by the specimens of the animal that, from time to time were casting up. The winged appendages of the sides of the head, as movable fins, had easily given rise to a variety of opinions concerning their true affinities, and which, says M. Agassiz, “have been regarded by the most able naturalists successively as Tortoises, Fishes, Crustacea, and even Coleoptera.” The fossils of Dura Den were at first regarded by him as belonging to the type as well as genus Pterichthys, and my specimens were actually returned from Neufchâtel so named—the “broad” and “narrow” species—and the label still remains attached. Meanwhile, five or six species of the genus Pterichthys had been already determined and described by him, from the fossils of Cromarty and Morayshire—these in the collection chiefly of Mr. Hugh Miller; and Mr. Miller being, about the same period, engaged in the preparation of his work, “The Old Red Sandstone,” speedily under the new nomenclature, as he was so opportunely furnished with the materials, gave the public the benefit of M. Agassiz’s discovery and version of their true and authentic history. What we had hastily, certainly, but still influenced much in the matter by the judgment of others, referred to the order of Coleoptera, he was enabled at once, upon the inspection of a Dura Den specimen, and from its very striking resemblance to his own, to pronounce to be a Pterichthys. A few pages before he had stated that he could make nothing of the creature, although some specimens of the fossil had been in his possession for a period of nearly ten years; but NOW, he was able to record,—“I very lately enjoyed the pleasure of examining the _bona fide_ ichthyolite itself,—one of the specimens of Dura Den, and apparently one of the more entire, in the collection of Professor Fleming. Its character as a Pterichthys I found very obvious.” But short-lived, indeed, are all mundane enjoyments. The most intellectual, in the revolutions of science, are not exempt from their general character of vanity. While the two northern sages were thus gazing, in all the raptures of a new discovery, “upon the _bona fide_ ichthyolite _itself_,” the philosopher, under the shelter of the Jura, was doubting, re-examining, and finally correcting, his own first judgment; and, while the virgin pages of “The Old Red Sandstone” had scarcely time to reach their author, the “Monograph” was announcing to the world the determination of a new genus, and that the fossil of Dura Den was a Pamphractus, and no Pterichthys at all.