hose from between triple row of bayonetlike teeth
that curved inward like those of a shark, to splash and bubble freely
to the rock floor and to dribble horribly over the warty, gray hide.

Then Nelson discovered an amazing fact. About the great scaly neck,
thick as a boy's waist, was fastened a ponderous collar, set with
short, sharp spikes.

Nelson gasped. "What in hell!" he cried. "This damn thing's somebody's
property!" His mind, staggered at the thought of dealing with a race
that could and would domesticate such a hideous monster. "Well, it's
no use standing here," he muttered, wiping the sweat from his eyes.
"This isn't getting poor Alden away from those devils."

_Thud! thud!_ In the act of turning he paused, listened once more.
Then he discovered to his amazement that the heart of the apparently
dead reptile was still beating strongly. He could even see the yellow
skin of its belly rise and fall. The effect was grotesque, uncanny.

"Of course," muttered the shaken aviator, "I'd forgotten a reptile's
ganglions will keep on beating for hours, like that shark we killed
off Paumotu. Its heart didn't stop for five hours."

* * * * *

Leaving the slain allosaurus behind, the aviator limped onwards,
doggedly following a trail which wound down, ever onwards, into the
depths of the earth. Gradually the air became so filled with steam
that he stripped off his fur jumper and trousers. Clad in a khaki
flannel shirt, serge trousers and shoepacks, he paused long enough to
count his cartridges, and found there were just fourteen. Hell! Not
very many with which to venture into an unknown abyss. He distributed
them in his pockets, and, somewhat relieved of the weight of the fur
suit, took up his advance, playing the flashlight ahead of him as he
went.

"Poor Alden," he thought. "I wonder if he's still alive?"

Every moment expecting to stumble over the mangled corpse of his
friend he hurried on, making better time over the cavern floor, but
soon even the lighter clothing commenced to feel oppressive.

"Must be the earth's heat," he muttered, while the steam clouds rolled
by him like ghostly serpents. "Guess the crust is very thin
here--something like Yellowstone. Probably I'll find some thermal
springs ahead."

Just as he spoke the tunnel took a sharp turn to the right. He
scrambled around the bend to stand petrified, for with the suddenness
of lightning a flood of dazzling orange-red