The raft took a sudden turn, whirled round, entered another tunnel--this time illumined in a most singular manner. The roof was formed of porous stalactite, through which a moonlit vapor appeared to pass, casting its brilliant light upon our gaunt and haggard figures. The light increased as we advanced, while the roof ascended; until at last, we were once more in a kind of water cavern, the lofty dome of which disappeared in a luminous cloud! A rugged cavern of small extent appeared to offer a halting place to our weary bodies. My uncle and the guide moved as men in a dream. I was afraid to waken them, knowing the danger of such a sudden start. I seated myself beside them to watch. As I did so, I became aware of something moving in the distance, which at once fascinated my eyes. It was floating, apparently, upon the surface of the water, advancing by means of what at first appeared paddles. I looked with glaring eyes. One glance told me that it was something monstrous. But what? It was the great "shark-crocodile" of the early writers on geology. About the size of an ordinary whale, with hideous jaws and two gigantic eyes, it advanced. Its eyes fixed on me with terrible sternness. Some indefinite warning told me that it had marked me for its own. I attempted to rise--to escape, no matter where, but my knees shook under me; my limbs trembled violently; I almost lost my senses. And still the mighty monster advanced. My uncle and the guide made no effort to save themselves. With a strange noise, like none other I had ever heard, the beast came on. His jaws were at least seven feet apart, and his distended mouth looked large enough to have swallowed a boatful of men. We were about ten feet distant when I discovered that much as his body resembled that of a crocodile, his mouth was wholly that of a shark. His twofold nature now became apparent. To snatch us up at a mouthful it was necessary for him to turn on his back, which motion necessarily caused his legs to kick up helplessly in the air. I actually laughed even in the very jaws of death! But next minute, with a wild cry, I darted away into the interior of the cave, leaving my unhappy comrades to their fate! This cavern was deep and dreary. After about a hundred yards, I paused and looked around. The whole floor, composed of sand and malachite, was strewn with bones, freshly gnawed bones of reptiles and fish, with a mixture of mammalia. My very soul grew sick as my body shuddered with horror. I had truly, according to the old proverb, fallen out of the frying pan into the fire. Some beast larger and more ferocious even than the shark-crocodile inhabited this den. What could I do? The mouth of the cave was guarded by one ferocious monster, the interior was inhabited by something too hideous to contemplate. Flight was impossible!