TH E 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. X. — The Jurassic Formation on the Atlantic 

 Coast. — Supplement ,•* by O. C. Marsh. 



At the autumn meeting of the National Academy last year, 

 in New York, I made a communication entitled " The Jurassic 

 Formation on the Atlantic Coast."f In this paper I brought 

 together the results of a careful investigation which I had 

 been conducting for several years, going to prove that the 

 Jurassic formation, generally supposed to be wanting on the 

 Atlantic border, was represented by a definite series of strata 

 in the exact position where such deposits were to be expected. 

 Accompanying this communication, I exhibited a number of 

 drawings and sections illustrating the Jurassic deposits of the 

 West, which I had long before investigated and fully described ; 

 namely, the Baptanodon beds, consisting of marine Jurassic 

 strata with many characteristic fossils, mostly invertebrates, 

 and above these the fresh-water Atlantosaurus beds, which 

 have yielded such vast numbers of gigantic reptiles and other 

 characteristic vertebrates. Sections showing the relative posi- 

 tion of these deposits, with the strata above and below them 

 as they are seen at several localities in Wyoming and Colorado, 

 were also exhibited. 



In comparison with this great development of the Jurassic 

 in the West, I next discussed the so-called Potomac formation 

 in Maryland, in which I had found a corresponding vertebrate 

 fauna that proved the strata containing them to be also of 

 Jurassic age. I then gave a brief account of my researches 



* Abstract of communication made to the National Academy of Sciences, 

 Boston meeting, November 18, 1897. 



f This Journal, vol. ii, p. 438, December, 1896; and Science, vol. iv, p. 805, 

 December 4, 1896. See also, this Journal, vol. ii, p. 295, October, and p. 375, 

 November, 1896. 



-August, 1898. 



