Not mythological terrors but the ichthyosaurs, plesiosaurs, and mosasaurs, who lived in the sea ""millions of years ago, at the time of the dinosaurs,"" are the subject of this competently written and effectively illustrated rundown. Selsam describes several species, tells how we know that ichthyosaurs were born alive ""right into the sea,"" and notes that, just like the dinosaurs, they all disappeared about 70 million years ago--""Nobody knows why."" Throughout, this lacks the sense of inquiry that picked up Kaufman's corresponding Flying Reptiles in the Age of Dinosaurs (1976), but it's a sensible, well-structured catalog, with a wide audience waiting.