"Oh, we can camp anywhere," cried Tom. "It's good enough--just for one
night."

They began to trudge along the edge of the horseshoe curve, over smooth
sand. But this did not last, and presently they came to a muddy flat
and went down to their ankles. Dick was ahead and he cried to the
others.

"Stop! It's not fit to walk here!"

"Why, it's like a bog!" declared Sam, after testing it.

"We'll have to go inland a distance," said Tom. "Come on," and he
turned back and struck out for the palms and bushes beyond.

It was then that the Rover boys began to realize what was before them.
Scarcely had they penetrated the interior for fifty yards when they
found themselves in a perfect network of trailing vines. Then, after
having pulled and cut their way through for fifty yards more, they came
to a spot that was rocky and covered with a tangle of thorny bushes.

"Wow!" ejaculated Tom, after scratching his hand and his leg. "This is
something prime, I must confess!"

"What I call hunting a treasure with a vengeance," added Dick, dryly.

"I move we go back," came from Sam. "We seem to be stuck in more ways
than one."

"Perhaps it is better traveling just beyond," declared Dick. "I am not
going to turn back just yet anyway."

He took the lead, breaking down the thorny bushes as best he could, and
Sam and Tom followed closely in his footsteps. It was rather dark among
the bushes and almost before the three knew it they had fallen headlong
into a hollow.

"Well, I never!"

"This is coming down in a hurry!"

"Is this the treasure cave?"

Such were the exclamations of the three lads as they picked themselves
up out of the dirt, which, fortunately for them, was soft and yielding.
Nobody had been hurt, for which they were thankful.

The hollow was about fifty feet in diameter and half that depth in the
center. On the opposite side were more bushes and rocks, and then a
thicket of tall trees of a variety that was strange to them.

"This is what I call hard work," observed Tom, as they began to fight
their way along again. "I don't know but what we would have done as
well to have waited until morning."

"Don't croak, Tom," said Sam.

"Oh, I am not croaking, but this is no fun, let me tell you that."

All of the boys were panting from their exertions, and soon they had to
call a halt to get their breath. It was now growing dark rapidly, for
in the tropics there is little of what we know as twilight.

"We certainly