To a large number of people the name devil fish brings to mind a conception of an octopus, squid, cuttle fish, or a member of that species. This is, however, a mistake.

The true devil fish of the tropics is a member of the sting ray family, and the common name it bears is given to it because of two prongs, or horns, which project just in front of its mouth. His Satanic Majesty is popularly supposed to have horns, together with a tail, hoofs and other appendages, and the horns of this sting ray fish are what give it the name it bears.

The devil fish, some specimens of which grow to the weight of a ton and measure fifteen feet from wing tip to wing tip, are armed with a long tail, terminating in a tough, horny substance, like many of the ray family members. This horn-tipped tail, lashing about in the water, becomes a terrible weapon of defense. Possibly it is used for offense, as the devil fish feeds on small sea animals, sweeping them into its mouth by movements of the horns mentioned. These horns, swirled about in the water, create a sort of suction current, and on that the food fishes are borne into the maw of the gigantic creature.

A whale rushes through a school of small sea animals with open mouth, takes in a great quantity of water, and the fringe of whalebone acts as a strainer, letting out the water and retaining the food. In like manner the devil fish feeds, except that it has no whalebone. Its "horns" help it to get a meal.

The "wing tips" of the devil fish have been spoken of. They are not really wings, though when one of these fish breaks water and shoots through the air, it appears to be flying. The wings are merely fins, enormously enlarged, and these give the fish its great size, rather than does the body itself. It is the whipping spike-armed tail of the devil fish that is to be feared, aside from the fact that the rush of a monster might swamp a small boat.

It was two or three of these devil fish that were now floating in the water above Tom and his companions, who were grouped about the stern of the disabled submarine.

"They won't attack us unless we disturb them," said Tom through his telephone, speaking to Ned and Koku. "Keep still and they'll swim away. I guess they're trying to find out what new kind of fish our boat is."

All might have gone well had not Koku acted precipitately. One of the devil fish, the smallest of the trio, measuring about ten feet across, swam down near the giant. It was an uncanny looking creature, with its horns swirling about in the water and its bone-tipped tail lashing to and fro like a venomous serpent.

"Look out!" cried Tom. But he was too late. Koku raised his axe and struck with all his force at the sea beast. He hit it a glancing blow, not enough to kill it, but to wound it, and immediately the sea was crimsoned with blood.

The devil fish was able to observe under water better than its human enemies, and it was in no doubt as to its assailant. In an instant it attacked the giant, seeking to pierce him with the deadly tail.

These tails are not only armed with a tip of horn-like hardness, they are also poisonous, and their penetrating power is great. Fishermen have sometimes caught small sting rays, which are a sort of devil fish. Lashing about in the bottom of a boat a sting ray can send its tail tip through the sole of a heavy boot and inflict a painful wound which may cause serious results.

The beast Koku had wounded was trying to sting the giant, and the latter, aware of his peril, was striking out with the axe.

"Look out, Tom!" called Ned through his telephone, as he saw one of the two unwounded devil fish swirl down toward the young inventor. Tom looked up, saw the big, horrible shape above him, and jabbed it with the sharp, steel bar. He inflicted a wound which added further to the crimson tinge in the sea, and that fish now attacked Tom Swift.

In another instant all three divers were fighting the terrible creatures, that, knowing by instinct they were in danger, were using the weapon with which nature had provided them. They lashed about with their sharp-pointed tails, and more than one blow fell on the suits of the divers.

Had there been the least penetration, of course almost instant death would have followed. For the sea, at that depth and pressure, entering the suits would have ended life suddenly. But Tom had seen to it that the suits were well made and strong, with a lining of steel. And however great a thickness of leather the devil fish could send his sting through, it could not overcome steel.

There was danger, though, that the slender tip might slip through the steel bars across the windows in the helmets and shatter the glass. And that would be as great a danger as if the suits themselves were penetrated.

"We've got to fight 'em!" gasped Tom through his instrument, and, seeing his chance, he gave another jab to the devil fish attacking him. Koku, too, was standing up well under the attack of the monster he had first wounded. Ned, watching his chance, got in several blows, first at one and then at the other of the huge creatures. The third devil fish, which had not been wounded, had disappeared. Finally Koku, with a desperate blow, succeeded in severing the tail from the beast attacking him, and that battle was over.

As if realizing that it had lost its power to harm, the devil fish at once swam off, grievously wounded. Then Koku turned his attention to Tom's enemy. Ned, too, lent his aid, and they succeeded in wounding the creature in several places, so that it sank to the bottom of the sea and lay there gasping.

Slowly the red waters cleared and the three divers, exhausted by the fight, could view the remaining creature--the one wounded to death. It was the largest of the three, and truly it was a monster. But it was past the power to harm, and in a few minutes an under sea current carried it slowly away. Later it would float, doubtless, or be devoured by sharks or other ocean pirates before reaching the surface.

"Thank goodness that's over!" said Ned to Tom. "I don't want to see any more of them."

"There may be more about," Tom said. "We'd better keep watch. Ned, you lay off and Koku and I will work on the propellers. Then you can take your turn."

This plan was followed. Koku, not being tired, did not need to stop working, and he was the first to free his shaft partially of the entangling weeds. Tom rapped a signal, the blades were slowly revolved and then came free. A little later the second was in like condition.

"Now we can move!" said Tom, as they started back toward the diving chamber. "I hope we don't run into another patch of that serpent grass."

"Nor see any more devil fish," added Ned.

"Same here!" echoed the young inventor.

Luck seemed to be with the gold-seekers after that, for as the submarine was sent ahead, no more of the long, entangling grass was encountered.

The search for the sunken Pandora was now begun in earnest, since they were positive that they were at the right spot.

No immediate sign of her was found. But Tom and his friends hardly expected to be as lucky as that. They were willing to make a search. For, as Tom had said, a current might have shifted the position of the wreck.

They followed the plan of moving about in ever-widening circles. Only in this way could they successfully cover the ground. It was the third day after the encounter with the devil fish that Tom, Ned and Mr. Damon were in the forward observation cabin. The eccentric man suddenly pointed to something visible from the starboard window.

"There's a wreck, Tom!" he cried. "Maybe it's the Pandora!"

Tom and the others hurried to Mr. Damon's side and peered out into the sea, illuminated by the great searchlight.

"That isn't the Pandora!" said the young inventor.

"But it's a wreck, isn't it?" asked Ned.

"Yes, it's a sunken vessel, all right," Tom assented. "But it's a reminder of the Great War. Look! She has been blown up by a torpedo!"