82 A CENTUEY OF SCIENCE 



Above lie the dinosaur-bearing fresh-water deposits, 

 since 1894 known as the Morrison beds. In 1896, 0. C. 

 Marsh (1831-1899) announced the presence of Jurassic 

 fresh-water strata along the Atlantic coast (2, 433), but 

 to-day only a small part of them are regarded as of the 

 age of the Morrison, while the far greater part are 

 referred to the Comanche or Lower Cretaceous. The 

 red beds below the Jurassic of the Rocky Mountain area 

 have during the past twenty years been shown to be in 

 part of Upper Triassic age and of fresh-water origin, 

 while the greater lower part is connected with the Car- 

 boniferous series and is made up of brackish- and fresh- 

 water deposits of probable Permian time. 



Triassic of Atlantic States. The fresh-water Triassic 

 of the Atlantic border states was first mentioned by 

 Maclure (1817), who regarded it as the equivalent of the 

 Old Red Sandstone of Europe. In this he was followed 

 by Hitchcock in 1823 (6, 39), the latter saying that above 

 it lies "the coal formation," which is true for Europe, 

 but in America the coal strata are older than these red 

 beds, now known to be of Triassic age. 



The first one to question this correlation was Alex- 

 andre Brongniart, who had received from Hitchcock rock 

 specimens and a fossil fish which he erroneously identi- 

 fied with a Permian species, and accordingly referred 

 the strata to the Permian (3, 220, 1821 ; 6, 76, pi. 9, figs. 1, 

 2, 1823). The discerning Professor Finch in 1826 

 remarked that the red beds of Connecticut appear to 

 belong "to the new or variegated sandstone, " because of 

 eight different criteria that he mentions. Of these, but 

 two are of value in correlation, their "geological posi- 

 tion" and the presence of bones other than fishes. In 

 the Connecticut area, however, the geological position 

 cannot be determined even to-day, and in Finch's time 

 the bones of dinosaurs were unknown. Finch then goes 

 on to point out the occurrences of Old Red Sandstone in 

 Pennsylvania, but all of the places he refers to are either 

 younger or older in time. Here we again see the fatality 

 of trying to make positive correlations on the basis of 

 lithology and color (10, 209, 1826). In 1835, however, 

 Hitchcock showed that the bones that had been found in 

 1820 were those of a saurian, and accordingly referred 



