At length, unable to bear the strain longer, he flung open the door, and stepped out on to the deck.

For some time he paced to and fro, the ring of his boots upon the steel plates sounding cheerily in his ears.

Then suddenly he paused in his stride, and glanced sharply astern.

One hundred yards away a strange, rippling eddy appeared on the swell of the heaving water.

Remembering that the attack of the octopus had been heralded in like fashion, Wilson bolted into the turret and closed the door. A moment later, with face pressed against the glass, he was watching eagerly for developments.

“If it’s another squid,” he muttered, “I’m afraid he’s a trifle too late. That ripple gives the show away. By Jove! he’s keeping it up,” looking with surprise at the violently eddying water.

Still the water boiled and hissed and foamed, racing round in an ever-increasing circle.

Then, “Great Heaven!” burst from the lips of the engineer. “Ichthyosaurus!”

Up in the midst of the eddy, with a rush and a swirl, appeared a monstrous reptile. Never before had the engineer seen aught to equal the thing; yet instinctively he knew what the creature was, recognised it in an instant as the great fish-lizard, that old inhabitant of the prehistoric seas.

Full two hundred feet the reptile was in length, and its body was covered with great, overlapping, scaly plates. The gaping jaws revealed a double row of yellow fangs, and its monstrous eyes glowed like moons, as the brute fixed them curiously upon the motionless vessel.