I'rof. 0. C. Marsh — A Neio American Jurassic Dinosaur. 99 



Shortly after Endolph Ludwig made a journey to the Ural 

 Mountains, and explored especially the series of rocks considered 

 by Murchison as his tyi^ical formation of the ' Permian ' in the 

 Government of Perm. He soon recognized the errors of super- 

 positions, classifications and determinations of ages committed by 

 his predecessors, and having convinced himself there on the field 

 that Murchison by mistake has placed in his 'Permian System' the 

 whole of the Trias, he published successively his Geogenische unci 

 geognostiscJie Studien auf einer Beise durcli Bussland tind den Ural, 

 with a Geological Map of a part of the Government of Perm ; ^ and 

 his Geological Map, Die Dyas in Bussland, in the beautiful and 

 excellent monograph of the Di/as, by H. B. Geinitz, 1861 and 1862. 



Other discoveries followed ; and now even in Russia the word 

 * Dyas ' is used, as more appropriate than any other offered until 

 now, to designate a series of rocks, so well known and distinguished 

 in Germany under the double appellation of Rothe-todte-liegende 

 or Rothliegende and Zechstein. 



The celebrated Russian geologist, the late Edouard d'Eichwald, 

 has signalized and pointed out the Government of Orenburg as 

 better fitted to give a fine series of the Dyassic rocks than the 

 Government of Perm, long before Mr. W. H. Twelvetrees ; for we 

 read in his introduction to vol. i. part 2, of his Lethea Bosstca, p. 17, 18, 

 Stuttgart, 1860: " The Permian System is the same as the Peneen, 

 which is better worth preserving as a geological name, than Per- 

 mian, especially as the animals and plants characteristic of the 

 Peneen System are not found in the Government of Perm, but in 

 that of Orenburg." " In the Lethea, I have sometimes called these 

 strata Cupriferous sandstones, sometimes Magnesian or Zechstein, 

 limestone whicb is interpolated between the beds of Cupriferous 

 sandstone : thus well deserving the name of ' Dyas ' suggested by 

 M. J. Marcou." 



Finally, Prof. C. Greveingk uses the word Dyas in his description 

 and on his large Geognostische Karte der Osiseeprovince Liv.-EsL- 

 und Kurland, Dorpat, 1879. 



Cambridge, Massachusetts, U.S.A. 



II. — On the DiPioDOcrD^, a New Pamiit oe the Satjuopoda; an 

 Oeder of Ameeican Jueassic Dinosatjes.^ 



By Professor 0. C. Marsh, M.A., F.G.S. 



THE Sauropocla are now generally recognized by anatomists as a 

 well-marked order of the Sub-class Dinosauria. In the previous 

 articles of this series, the main characters of the two families of this 

 order [AtlantosaiiridcB and Morosauridce) already named by the writer 

 liave been given.^ A third family is represented by the genus 



1 The city of Perm, which has given its name to the Government of Perm and to 

 the ' Permian System,' is not built on the so-called ' Permian,' but on the Trias. 



■^ From the American Journal of Science, vol. xxvii. February, 1884, pp. 161-168. 



3 See Silliman's American Journal of Science, vol. xvi. p. 411, Nov., 1878 ; vol. 

 xvii. p. 86, Jan., 1879 ; vol. xxi. p. 417, May, 1881 ; vol. xxiii. p. 81, Jan., 1882 ; 

 and vol. xxvi. p. 81, Aug., 1883. 



