SCALE OF HOLOPTYCHIUS GIGANTEUS.
(Nat. size.)
(Old Red Sandstone.)
SECTION OF SCALE OF HOLOPTYCHIUS.
(Mag. eight diameters.)
A brief anecdote, yet further illustrative of the framework of this ancient ganoid, may throw some additional light on what I have ventured to term the human cast of the contrivances exhibited in the organisms of the old geologic ages. After carefully examining many specimens, I published a restoration of both the upper and under side of Pterichthys fully fifteen years ago. The greatest of living ichthyologists, however, misled by a series of specimens much less complete than mine, differed from me in my conclusions; and what I had represented as the creature's under or abdominal side, he represented as its upper or dorsal side; while its actual upper side he regarded as belonging to another, though closely allied, genus. I had no opportunity, as he resided on the Continent at the time, of submitting to him the specimens on which I had founded; though, at once certain of his thorough candor and love of truth, and of the solidity of my data, I felt confident that, in order to alter his decision, it was but necessary that I should submit to him my evidence. Meanwhile, however, the case was regarded as settled against me; and I found at least one popular and very ingenious writer on geology, after referring to my description of the Pterichthys, going on to say that, though graphic, it was not correct, and that he himself could describe it at least more truthfully, if not more vividly, than I had done. And then there followed a description identical with that by which mine had been supplanted. Five years had passed, when one day our greatest British authority on fossil fishes, Sir Philip Egerton, was struck, when passing an hour among the ichthyic organisms of his princely collection, by the appearance presented by a central plate in the cuirass of the Pterichthys. It is of a lozenge form, and, occupying exactly such a place in the nether armature of the creature as that occupied by the lozenge shaped spot on the ace of diamonds, it comes in contact with four other plates that lie around it, and represent, so to speak, the white portions of the card. And Sir Philip now found, that instead of lying over, it lay under, the four contiguous plates: they overlapped it, instead of being overlapped by it. This, he at once said, on ascertaining the fact, cannot be the upper side of the Pterichthys. A plate so arranged would have formed no proper protection to the exposed dorsal surface of the creature's body, as a slight blow would have at once sent it in upon the interior framework; but a proper enough one to the under side of a heavy swimmer, that, like the flat fishes, kept close to the bottom;—a character which, as shown by the massive bulk of its body, and its small spread of fin, must have belonged to the Pterichthys. Sir Philip followed up his observations on the central plate by a minute examination of the other parts of the creature's armature; and the survey terminated in a recognition of the earlier restoration,—set aside so long before,—as virtually the true one;—a recognition in which Agassiz, when made acquainted with the nature of the evidence, at once acquiesced. Now, here was there a question which had been raised regarding the true mechanism of one of the oldest ganoidal fishes, and settled erroneously on wrong data, again opened up, to be settled anew on one of the most obvious mechanical principles exemplified in the simple art of the slater or tiler. The argument of Sir Philip amounted simply to this:—If the accepted restoration be a true one, then the Creator of the Pterichthys must have committed a mistake in mechanics which an ordinary slater would have avoided; but as the Creator commits no such blunders, the mistake probably occurs in but the restoration. I may mention, that the dorsal surface of this ancient fish had also its central plate,—a lozenge truncated at its two longer ends; and that, moulded to meet the necessities of its position, it was not flat, like the under one, but strongly arched; and that on four of its six sides it overrode by a squamose suture the lower plates with which it came in contact.
These are but humble illustrations of the designing principle, as exhibited of old; and yet they impress none the less strongly on that account. Among the many contrivances of the Chinese Museum, to which I have already referred, none seemed more to excite the curiosity of visitors than a set of tall-backed, elaborately carved chairs, exceedingly like those which were used in our own country two centuries ago, and which Cowper so exquisitely describes. For thousands of miles in the wide tract that spreads out between European Christendom and the great wall, the inhabitants squat upon mats or carpets, or loll on divans; and the contrivance of the chair is unknown: it reappears in China, however, and reappears, not as a mere seat or stool, but as, in every bar and limb, the identical chair of Europe arrested a century or two back in its development. And every corresponding tenon and mortise exhibited by the Chinese and European examples of this simple piece of furniture served more forcibly to show an identity of character in the minds which had originated them in countries so far apart, than the more elaborate contrivances which, though illustrative of the same principles of invention, were less easily understood. It is so with the more simple and familiar instances of adaptation furnished by the works of the Creator. We infer from them, more directly than from the complex mechanisms, that he who wrought of old after the manner of a man must have, in his intellectual character, if I may so express myself, certain man-like qualities and traits. In all those works on Natural Theology that treat, like the work of Paley, on the argument of design, the assumption of a certain unity of the intellectual nature of the Creator and creature is made, tacitly at least, the basis of all the reasonings; and it is in the cases in which the design is most simple that the argument is most generally understood. It is in the lower skirts of the Divine nature that we most readily trace the resemblance to the nature of man,—an effect, mayhap, of the narrow reach of our faculties in their present infantile state.
