of the great Conglomerate,
I found what I sought,--a well-marked bone, perhaps the oldest
vertebrate remain yet discovered in Orkney, embedded in a light
grayish-colored layer of hard flag.

What, asks the reader, was the character of the ancient denizen of the
Palaeozoic basin of which it had formed a part? Was it a large or small
fish, or of a high or low order? Not certainly of a low order, and by no
means of a small size. The organism in the rock was a specimen of that
curious nail-shaped bone of the Asterolepis which occurs as a central
ridge in the single plate that occupies in this genus the wide curve of
the under jaw, and as it was fully five inches in length from head to
point, the plate to which it belonged must have measured ten inches
across, and the frontal occipital buckler with which it was associated,
one foot two inches in length (not including the three accessory plates
at the nape), by ten inches in breadth. And if built, as it probably
was, in the same massy proportions as its brother Coelacanths the
Holoptychius or Glyptolepis, the individual to which the nail-shaped
bone belonged must have been, judging from the size of the corresponding
parts in these ichthyolites, at least twice as large an animal as the
splendid Clashbennie Holoptychius of the Upper Old Red, now in the
British Museum. The bulkiest icthyolites yet found in any of the
divisions of the Old Red system are of the genus Asterolepis; and to
this genus, and to evidently an individual of no inconsiderable size,
this oldest of the organisms of the Orkney belonged. I was so interested
in the fact, that before leaving this part of the country, I brought Dr.
Garson, Stromness, and Mr. William Watt, jun., Skaill, both very
intelligent palaeontologists, to mark the place and character of the
fossil, that they might be able to point it out to geological visitors
in the future, or, if they preferred removing it to their town Museum,
to indicate to them the stratum in which it had lain. For the present, I
merely request the reader to mark, in the passing, that the most ancient
organic remain yet found in the Old Red of this part of the country,
nay, judging from its place, one of the most ancient yet found in
Scotland,--so far as I know, absolutely the _most_ ancient,--belonged to
a ganoid as bulky as a large porpoise, and which, as shown by its teeth
and jaws, possessed that peculiar organization which characterized the
reptile fish of the Upp