"No, Marty," Levine said. "It's not an iguana."

"Before you say anything more," Guitierrez said, glancing at the pilot, "I think you ought to know that several previously unknown species of lizard have shown up in this area. Nobody's quite sure why. Perhaps it's due to the cutting of the rain forest, or some other reason. But new species are appearing. Several years ago, I began to see unidentified species of - "

"Marty. It's not a damn lizard."

Guitierrez blinked his eyes. "What are you saying? Of course it's a lizard."

"I don't think so," Levine said.

Guitierrez said, "You're probably just thrown off because of its size. The fact is, here in Costa Rica, we occasionally encounter these aberrant forms - "

"Marty," Levine said coldly. "I am never thrown off "

"Well, of course, I didn't mean that - "

"And I am telling you, this is not a lizard," Levine said.

"I'm sorry," Guitierrez said, shaking his head. "But I can't agree."

Back at the white helicopter, the men were huddled together, putting on white surgical masks.

"I'm not asking you to agree," Levine said. He turned back to the carcass. "The diagnosis is settled easily enough, all we need do is excavate the head, or for that matter any of the limbs, for example this thigh here, which I believe - "

He broke off, and leaned closer. He peered at the back of the thigh.

"What is it?" Guiltierrez said.

"Give me your knife."

"Why?" Guitierrez said.

"Just give it to me."

Guitierrez fished out his pocketknife, put the handle in Levine's outstretched hand. Levine peered steadily at the carcass. "I think you will find this interesting."

"What?"

"Right along the posterior dermal line, there is a - "

Suddenly, they heard shouting on the beach, and looked up to see the men from the white helicopter running down the beach toward them. They carried tanks on their backs, and were shouting in Spanish.