"An electric ray. They carry enough electricity in them to run a small
lamp, and when they wish they can give you a powerful shock. They kill
their prey that way."

"Ouch--," exclaimed the professor, who had by this time got up, "the
ray nearly killed me. Let me look at the brute so that I'll know one
of them again."

"Why don't you put him in your collection?" asked Frank with a smile,
although his arm still hurt him where the electric ray had shocked it.

"I want no such fish as that round me, sir," said the professor
indignantly, and ordered Ben to throw the creature overboard with his
boat-hook.

After supper that night the boys hung about the decks till bedtime.
The hours passed slowly and they amused themselves by watching the
moonlit shores and speculating on the whereabouts of the Patagonians.

Suddenly Billy seized Frank's arm.

"Look," he exclaimed, pointing to a low ridge that stood out blackly
in the moonlight.

Behind the low eminence Frank could distinctly see a head cautiously
moving about, seemingly reconnoitering the two ships. In a few seconds
it vanished as the apparent spy retreated behind the ridge.

"That must have been a Patagonian," said Frank.