Marsh — Jurassic Formation on the Atlantic Coast. Ill 



Had this critic read the whole of my paper, he would have 

 found the following statement bearing on this point : 



"The Jurassic age of the Atlantosanrus beds of the West has 

 now been demonstrated beyond question by the presence of a 

 rich fauna of mammals, birds, reptiles, and fishes. Among these, 

 the Sauropoda were dominant, and the other Dinosaurs well 

 represented. 



' In the Potomac beds of Maryland, the same Jurassic verte- 

 brate fauna is present, as shown by the remains of five different 

 orders of reptiles already discovered in them. Among the Dino- 

 saurs are the Sauropoda, the Theropoda, and the Predentata, the 

 first group represented by several genera and a great Dumber of 

 individuals. One of these genera is Pleurocoelus, which has also 

 been found in the Jurassic of the West. Besides the Dinosaurs, 

 characteristic remains of Grocodilia and Testudinata are not 

 uncommon, and various Fishes have been found. The remains of 

 these six groups already known are amply sufficient to determine 

 the age of the formation, and still more important discoveries 

 doubtless await careful exploration."* 



Mr. Gilbert's next statement, which is likewise without real 

 foundation, is as follows : 



" The conclusion that the Atlantosanrus and other horizons of 

 the Rocky Mountain region are Jurassic was announced in the 

 same way, without citation of evidence." 



The announcement of the Atlantosaurus beds as Jurassic 

 was accompanied by a section showing their exact position in 

 the geological scale, and the characteristic genera of Reptilia 

 which then indicated their Jurassic age.f This was followed 

 by descriptions in rapid succession of many other vertebrate 

 fossils, proving beyond question that the horizon was Jurassic. 

 The Baptanodon beds were also defined, and their position in 

 the geological series established by characteristic fossils. The 

 demonstration on this point, I have already given above, and 

 need not repeat here. 



Another point needs correction, as Mr. Gilbert evidently 

 consulted my recent classification of the Dinosauria% without 

 appreciating the evidence it. contained. This is shown by the 

 following quotation from his review : 



" The closest affinity of the European and American formations 

 seems to be expressed by the statement that there is one Ameri- 

 can genus which falls in the same family with a European genus." 



* This Journal, vol. ii, p. 445, 1896. 



f Proceedings American Association, Nashville meeting, p 220, 1878; see also 

 Popular Science Monthly, p. 520, March, 1878. 



X The Dinosaurs of North America, 16th Annual Report, U. S. Geological 

 Survey, p. 238, 1896. 



