Presently a door in one side of the arena wall was opened to admit a huge, shaggy, bull-like creature.

“A Bos,” whispered Perry, excitedly.  “His kind roamed the outer crust with the cave bear and the mammoth ages and ages ago.  We have been carried back a million years, David, to the childhood of a planet—­is it not wondrous?”

But I saw only the raven hair of a half-naked girl, and my heart stood still in dumb misery at the sight of her, nor had I any eyes for the wonders of natural history.  But for Perry and Ghak I should have leaped to the floor of the arena and shared whatever fate lay in store for this priceless treasure of the Stone Age.

With the advent of the Bos—­they call the thing a thag within Pellucidar—­two spears were tossed into the arena at the feet of the prisoners.  It seemed to me that a bean shooter would have been as effective against the mighty monster as these pitiful weapons.

As the animal approached the two, bellowing and pawing the ground with the strength of many earthly bulls, another door directly beneath us was opened, and from it issued the most terrific roar that ever had fallen upon my outraged ears.  I could not at first see the beast from which emanated this fearsome challenge, but the sound had the effect of bringing the two victims around with a sudden start, and then I saw the girl’s face—­she was not Dian!  I could have wept for relief.

And now, as the two stood frozen in terror, I saw the author of that fearsome sound creeping stealthily into view.  It was a huge tiger—­such as hunted the great Bos through the jungles primeval when the world was young.  In contour and markings it was not unlike the noblest of the Bengals of our own world, but as its dimensions were exaggerated to colossal proportions so too were its colorings exaggerated.  Its vivid yellows fairly screamed aloud; its whites were as eider down; its blacks glossy as the finest anthracite coal, and its coat long and shaggy as a mountain goat.  That it is a beautiful animal there is no gainsaying, but if its size and colors are magnified here within Pellucidar, so is the ferocity of its disposition.  It is not the occasional member of its species that is a man hunter—­all are man hunters; but they do not confine their foraging to man alone, for there is no flesh or fish within Pellucidar that they will not eat with relish in the constant efforts which they make to furnish their huge carcasses with sufficient sustenance to maintain their mighty thews.

Upon one side of the doomed pair the thag bellowed and advanced, and upon the other tarag, the frightful, crept toward them with gaping mouth and dripping fangs.

The man seized the spears, handing one of them to the woman.  At the sound of the roaring of the tiger the bull’s bellowing became a veritable frenzy of rageful noise.  Never in my life had I heard such an infernal din as the two brutes made, and to think it was all lost upon the hideous reptiles for whom the show was staged!