From beds definitely known as Lower Cretaceous (Trinity) in Oklahoma, a few bones of a sauropod dinosaur are known, and from nearly corresponding rocks in southern Kansas, plesiosaurs, crocodiles, turtles, and carnivorous dinosaurs are known from sparse remains. Doubtless the Potomac beds of Virginia, which have yielded bones of various dinosaurs, are also of Lower Cretaceous age. [Illustration: FIG. 30.—Restoration of _Casea_, a theromorph reptile from the Permian of Texas, about four feet long.] With the exception of a single vertebra of doubtful affinities and the cast of a turtle-shell no vertebrate fossils have ever been discovered in the extensive sandstones of Dakota age, the lowermost of the Upper Cretaceous. From the next horizon above the Dakota, the Benton Cretaceous, chiefly marine limestones, at least three genera of plesiosaurs are known from Kansas, Texas, and Arkansas, with two or three more from the limestone shales of Wyoming. A few specimens of armored dinosaurs, two genera of ancient crocodiles, nearly the last of their kind, some marine turtles, and a few vertebrae of ichthyosaurs, the last of the order known anywhere in the world, are also known from the Benton Cretaceous of Wyoming. Continuous with the Benton limestones above in Kansas are the famous beds of Niobrara chalk; perhaps no fossil deposits in the world are more famous. Exposures covering hundreds of square miles in western Kansas, almost pure chalk, have furnished fossil-hunters during the past forty years literally thousands of specimens of mosasaurs, hundreds of pterodactyls, and scores of plesiosaurs and marine turtles, in addition to the famous birds with teeth and countless fishes of diverse kinds. Two or three specimens of spoon-billed dinosaurs have been found in these deposits, but no other reptiles of any kinds. Beds of like age in Colorado and New Mexico have furnished a few specimens of mosasaurs. From the marine beds of Fort Pierre age, next above the Niobrara in the west, have come some excellent specimens of two genera of mosasaurs, three or four forms of plesiosaurs, a few pterodactyls, the largest of all marine turtles, and still fewer specimens of dinosaurs, in Kansas, South Dakota, Wyoming, and Montana. From deposits of approximately like age in Mississippi, Alabama, and New Jersey, many incomplete specimens were found years ago of mosasaurs, plesiosaurs, and turtles, the last of the amphicoelian crocodiles, the first of the procoelian crocodiles, and the famous specimen of _Hadrosaurus_ which served for the Hawkins restoration, the first attempt of its kind.