Atlantosaurus, the best known genera of the Sa~ tropoda hitherto found in American
deposits.* The fortunate discovery of a nearly complete skeleton of B1'ontosaurus has
added lIlany new points to our knowledge of this group, and some of these are given in the
present comlllunication. A second species, equally gigantic in size, has since been found,
and its distinguishing features al'e also here recorded. Two new genera from the same
formation are noticed, and an outline of classification of the best known American Jurassic …

ON the flanks of the Rocky Mountains, a narrow belt of strata can be traced for several
hundred miles, marked always by the bones of gigantic Dinosaurs. Its position is above the
characteristic red Triassic beds, and immediately below the hard sandstone of the Dakota
group. Hayden, Cope and others have regarded this horizon as Cretaceous, but the
abundant vertebrate remains now known from it prove its Jurassic age beyond a reasonable
doubt. The writer examined a typical outcrop of this series, on the western slope of tlie …