some basic work done."

"Eh?"

"You say this is a tilted block. In lowest formations right now. I'd like to get photos and if possible specimens of as many different varieties of shellfish as possible, at each level. Then it may be possible to set up some sort of temporal sequence—and use the things as index fossils if animals do evolve on this be-nighted mudball. If you could get me some radioactive dates at two or three nicely scattered levels, it would also help."

"Thanks," returned Lampert drily. "I could use material like that myself. I can tell you what you probably already know—you're not likely to get anything of the sort from limestone."

"Well—intrusions are always possible."

"You watch for 'em, then." The pair went to work.

Two hours out, a little more than one back. There was no one at the helicopter when they reached it, but the other group came in only a few minutes over the four-hour limit which Lampert had imposed. A comparison of notes over the meal which had been quickly prepared indicated that the second group had gone farther in point of miles covered, but had accomplished less work. Krendall had had the same idea as Sulewayo. But he had not attempted to carry it out since his canyon did not cut across the range, and would presumably not furnish a continuous change in formations.

Lampert and Sulewayo, as it happened, had not found any evidence of change themselves. The last fossils they had found were at least superficially identical with the first. There was the usual evidence of bedding, and it had been quite evident geometrically that the walk had taken them to originally higher, and presumably later, levels; but in what must have been eight hundred feet or more of original deposit, there seemed to have been no significant change in the fossil life. What eight hundred feet would mean in point of time, of course, no one had the least idea. There was not even a good guess as to how fast carbonates might be expected to precipitate in a Viridian ocean. Anyone could compute the carbonate ion equilibrium between atmosphere and sea, but no one knew anything to speak of about carbonate-precipitating organisms of the planet.

Mitsuitei changed the subject slightly at this point.

"We found several of the joints you predicted," he said to Lampert.

"Oh? Very wide? We 

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