Early in the boring the sandstone had given
place to a vein of Comanchean limestone, full of minute fossil
cephalopods, corals, echini, and spirifera, and with occasional
suggestions of siliceous sponges and marine vertebrate bones--the
latter probably of teliosts, sharks, and ganoids. This, in itself, was important enough, as affording the first
vertebrate fossils the expedition had yet secured; but when shortly
afterward the drill head dropped through the stratum into apparent
vacancy, a wholly new and doubly intense wave of excitement spread
among the excavators. A good-sized blast had laid open the subterrane secret; and now,
through a jagged aperture perhaps five feet across and three feet
thick, there yawned before the avid searchers a section of shallow
limestone hollowing worn more than fifty million years ago by the
trickling ground waters of a bygone tropic world. The hollowed layer was not more than seven or eight feet deep, but
extended off indefinitely in all directions and had a fresh, slightly
moving air which suggested its membership in an extensive subterranean
system. Its roof and floor were abundantly equipped with large
stalactites and stalagmites, some of which met in columnar form. But important above all else was the vast deposit of shells and bones,
which in places nearly choked the passage. Washed down from unknown
jungles of Mesozoic tree ferns and fungi, and forests of Tertiary
cycads, fan palms, and primitive angiosperms, this osseous medley
contained representatives of more Cretaceous, Eocene, and other
animal species than the greatest palæontologist could have counted or
classified in a year. Mollusks, crustacean armor, fishes, amphibians,
reptiles, birds, and early mammals--great and small, known and unknown. No wonder Gedney ran back to the camp shouting, and no wonder every one
else dropped work and rushed headlong through the biting cold to where
the tall derrick marked a new-found gateway to secrets of inner earth
and vanished æons. When Lake had satisfied the first keen edge of his curiosity he
scribbled a message in his notebook and had young Moulton run back to
the camp to dispatch it by wireless. This was my first word of the discovery, and it told of the
identification of early shells, bones of ganoids and placoderms,
remnants of labyrinthodonta and thecoiidea, great mosasaur skull
fragments, dinosaur vertebræ and armor plates, pterodactyl teeth and
wing bones, Archaeopteryx débris, Miocene sharks' teeth, primitive
bird skulls, and other bones of archaic mammals such as Palæotheres,
Xiphodons, Eohippi, Oreodons, and Titanotheriidæ. There was nothing as recent as a mastodon, elephant, true camel, deer,
or bovine animal; hence Lake concluded that the last deposits had
occurred during the Oligocene Age, and that the hollowed stratum had
lain in its present dried, dead, and inaccessible state for at least
thirty million years. On the other hand, the prevalence of very early life forms was singular
in the highest degree. Though the limestone formation was, on the
evidence of such typical imbedded fossils as ventriculites, positively
and unmistakably Comanchean and not a particle earlier; the free
fragments in the hollow space included a surprising proportion from
organisms hitherto considered as peculiar to far older periods--even
rudimentary fishes, mollusks, and corals as remote as the Silurian or
Ordovician. The inevitable inference was that in this part of the world there had
been a remarkable and unique degree of continuity between the life of
over three hundred million years ago and that of only thirty million
years ago. How far this continuity had extended beyond the Oligocene
Age when the cavern was closed was of course past all speculation. In any event, the coming of the frightful ice in the Pleistocene some
five hundred thousand years ago--a mere yesterday as compared with the
age of this cavity--must have put an end to any of the primal forms
which had locally managed to outlive their common terms. *       *       *       *       *

Lake was not content to let his first message stand, but had another
bulletin written and dispatched across the snow to the camp before
Moulton could get back. After that Moulton stayed at the wireless in
one of the planes, transmitting to me--and to the _Arkham_ for relaying
to the outside world--the frequent postscripts which Lake sent him by a
succession of messengers. Those who followed the newspapers will remember the excitement created
among men of science by that afternoon's reports--reports which have
finally led, after all these years, to the organization of that very
Starkweather-Moore Expedition which I am so anxious to dissuade from
its purposes. I had better give the messages literally as Lake sent
them, and as our base operator McTighe translated them from his pencil
shorthand:

    Fowler makes discovery of highest importance in sandstone and
    limestone fragments from blasts. Several distinct triangular
    striated prints like those in archæan slate, proving that source
    survived from over six hundred million years ago to Comanchean
    times without more than moderate morphological changes and decrease
    in average size. Comanchean prints apparently more primitive or
    decadent, if anything, than older ones. Emphasize importance of
    discovery in press. Will mean to biology what Einstein has meant
    to mathematics and physics. Joins up with my previous work and
    amplifies conclusions. Appears to indicate, as I suspected, that earth has seen whole cycle
    or cycles of organic life before known one that begins with
    Archæozoic cells. Was evolved and specialized not later than a
    thousand million years ago, when planet was young and recently
    uninhabitable for any life forms of normal protoplasmic structure. Question arises when, where, and how development took place. *       *       *       *       *

    Later. Examining certain skeletal fragments of large land and marine
    saurians and primitive mammals, find singular local wounds or
    injuries to bony structure not attributable to any known predatory
    or carnivorous animal of any period. Of two sorts--straight,
    penetrant bores, and apparently hacking incisions. One or two
    cases of cleanly severed bones. Not many specimens affected. Am
    sending to camp for electric torches. Will extend search area
    underground by hacking away stalactites. *       *       *       *       *

    Still later. Have found peculiar soapstone fragment about six inches
    across and an inch and a half thick, wholly unlike any visible local
    formation--greenish, but no evidences to place its period. Has
    curious smoothness and regularity. Shaped like five-pointed star
    with tips broken off, and signs of other cleavage at inward angles
    and in center of surface. Small, smooth depression in center of
    unbroken surface. Arouses much curiosity as to source and
    weathering.