The boys and Doctor Dan, seizing their rifles, ran that way, but before they got to the bend of the rocks they were able to see what was going on. It was such a combat as probably no man on earth ever witnessed before. There was old P. D. and a monster precisely similar to the one the boys had seen on the other side of the lake hard at it, and a bellowing and roaring broke upon the air that was fairly deafening. The Plesiosaurus would rear its ugly head far above the water and strike with lightning rapidity at its antagonist, which would dodge and then dart forward, squirting up two vast streams of water out of holes in each side of its huge snout, snapping its crocodile-like jaws and displaying its terrible teeth. For about twenty seconds the boys were treated to this wonderful exhibition and then, with a fearful splash, monster No. 2 leaped half its length out of the water, caught old P. D. by the neck and dragged him down out of sight. “By gracious!” cried Charley. “That’s great!” “Tremendous!” echoed Dick. “Who on earth ever saw the like?” “I’ll bet on old P. D. every time,” chuckled Doctor Dan, relaxing his gravity for once and indulging in a hearty laugh. “It don’t seem to strike you as comical as it does me, boys. It’s one of the funniest things I ever saw.” Dick failed to see where the laugh came in, but he said nothing and for some time they stood watching for the reappearance of the monsters, but the moments passed and they did not come to the surface again. “There must be more than one Plesiosaurus,” remarked Dick, as they sat at supper; “by the way, Doctor, you were going to tell us of your discovery and how we could capture old P. D.” “Why, there is a cove around on the western shore that has a very narrow entrance,” replied Doctor Dan. “There are great stones scattered all around there and there is one that I am sure would choke up the entrance if it was dropped between the ledges. Now if we could rig up some sort of a snare in the cove with the ropes we have brought and then pry the boulder over into the break and choke it up we would have our friend P. D. hard and fast.” “Always providing he is obliging enough to go into the cove and run into our snare,” said Dick. “Well, we will take a look at it in the morning and see what we can make out of it. I’m dead tired now and I’m going to turn in.” The tents had been moved further up the bank and as Doctor Dan had agreed to watch until morning Dick and Charley now wrapped themselves up in their blankets and put in a good night undisturbed. Doctor Dan had no news to report in the morning and after breakfast he went up on the ledges, wrapped himself in his blankets and went to sleep there, telling the boys that they need not trouble their heads about him, but just do whatever they pleased. “Let’s try the underground passage, Dick,” said Charley. “I’m wild to know if my theory is correct.”