A recently discovered rare piece of science fiction from the late, famous vertebrate paleontologist (1902-84), author of Discoverers of the Lost World (1984) and other scholarly nonfiction works. Here, in a brief story whose framework theory of time holds no more water than any other, ""chronologist"" (a physicist who studies time) Sam Magruder, while conducting an experiment in the year 2162, is hurled back in time to arrive, naked, 80 million years ago in the Cretaceous period of Earth's geological history. Magruder struggles to survive, to find food and shelter, avoid predators, clothe himself, and make fire, and finally records his experiences on stone tables that, luckily, are unearthed sometime after Magruder's original disappearance. Simpson's tale is well constructed and thoughtful but thin; of particular disappointment is his failure to invest the dinosaurs of the period with new or vibrant life: He adheres rigidly to the ""sluggish and dim-witted"" line, in painful contrast to such recent works as the progressive Robert T. Bakker's Raptor Red (p. 961). Of strictly limited appeal to the usual science fiction audience, though Simpson aficionados will heave nostalgic sighs as they leaf through.