Such, so far as the various hieroglyphics of the pile have yet rendered their meanings to the geologist, is the strange story recorded on the three-barred _pyramid_ of Stromness. I traced the formation upwards this evening along the edges of the upturned strata, from where the Great Conglomerate leans against the granite, till where it merges into the ichthyolitic flagstones; and then pursued these from older and lower to newer and higher layers, desirous of ascertaining at what distance over the base of the system its more ancient organisms first appear, and what their character and kind. And, embedded in a grayish-colored layer of hard flag, somewhat less than a hundred yards over the granite, and about a hundred and sixty feet over the upper stratum of the conglomerate, I found what I sought,—a well-marked bone,—in all probability the oldest vertebrate remain yet discovered in Orkney. What, asks the reader, was the character of this ancient organism of the Palæozoic basin? As shown by its cancellated texture, palpable to the naked eye, and still more unequivocally by the irregular complexity of fabric which it exhibits under the microscope,—by its speck-like life-points or canaliculi, that remind one of air-bubbles in ice,—its branching channels, like minute veins, through which the blood must once have flown,—and its general groundwork of irregular lines of corpuscular fibre, that wind through the whole like currents in a river studded with islands,—it was as truly osseous in its composition as the solid bones of any of the reptiles of the Secondary, or the quadrupeds of the Tertiary periods. And in form it closely resembled a large roofing-nail. With this bone our more practised palæontologists are but little acquainted, for no remains of the animal to which it belonged have yet been discovered in Britain to the south of the Grampians,[3] nor, except in the Old Red Sandstone of Russia, has it been detected any where on the Continent. Nor am I aware that, save in the accompanying wood-cut, (fig. 1,) it has ever been figured. The amateur geologists of Caithness and Orkney have, however, learned to recognize it as the “petrified nail.” The length of the entire specimen in this instance was five seven eighth inches, the transverse breadth of the head two inches and a quarter, and the thickness of the stem nearly three tenth parts of an inch. This nail-like bone formed a characteristic portion of the _Asterolepis_,—so far as is yet known, the most gigantic ganoid of the Old Red Sandstone, and, judging from the _place_ of this fragment, apparently one of the first. [Illustration: Fig. 1. INTERNAL RIDGE OF HYOID PLATE OF ASTEROLEPSIS.[4] (One third the natural size, linear.)]