was deposited, there's not much chance of land animals. However, we want as complete a chronological series as possible, so do the best you can on this level. We'll try for higher formations later. There should be plenty farther upriver, if this block is tilted the way it seems to be.

"String, perhaps you'd better go with Take and Hans. Set out when you're ready. Be back in—" he glanced automatically at the narrow strip of purplish-blue sky, then at his watch—"four hours; then we'll compare notes. After that we can either concentrate on one place or the other, or break out the boats and cross the streams, as indicated."

Twenty minutes later the parties were out of sight of each other and the helicopter. Lampert had spent the first few minutes of the walk wondering whether he had been too obvious in arranging for both the guide and Krendall to accompany the little archaeologist; but he quickly convinced himself that McLaughlin's speech had covered the arrangements pretty well.

In any case, he would probably have been distracted soon enough. The cliffs were interesting. Limestone, evidently, as expected—but rather dense, at that; maybe some barium replacing the calcium? or was the gravity different enough to destroy his judgement for such a small fragment? Probably not. He was actually using inertia more than weight in making his estimate. Anyway, the stuff was certainly a carbonate. It frothed satisfyingly under a drop of acid from Lampert's kit.

And there were fossils. Sulewayo's form was bent over a spot on the cliff face, examining minutely; but Lampert could see others from where he stood. None seemed remarkable. Most were rather evidently shellfish. He carefully refrained from giving them names according to the genera they resembled in Earth's rocks; Sulewayo and his colleagues frowned on the practice, which could be most misleading. He could not, however, resist the temptation to think of them as scallops.

"What do you have there, Ndomi?" He knew the other would not have spent so long on any shellfish.

"Not sure, precisely. Maybe vertebrate, maybe not. What could be armor and what could be ribs all mixed up. I think I'll mark it for future reference."

"I suppose it'll be another Devonian whatsit, like everything else on this planet, when you do decide."

"Pennsylvanian would better describe the world as a whole. Barring that, you may be right. Rob, if you'd give me a hand here we could get 

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