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APPENDIX. 
Art. XLIV.—Principal Characters of American Jurassic 
Dinosaurs ; by Professor O. C. MARSH. 
Part I. With seven Plates. 
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. Tts 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 verte- 
rate 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 the mountains in 
yoming, in 1868, and determined it to be Jurassic; and he 
has recently named the series the Atlantosaurus beds, from the 
most striking vertebrates they contain. e strata consist 
mainly of estuary deposits of shale and sandstone, and the hori- 
Zon 18 clearly upper Jurassic, as shown in the accompanying 
section (Plate [V.)* 
Besides the Dinosaurs, which are especially abundant, num- 
crous remains of Crocodilia (Diplosaurus), as well as Tortoises 
known from these beds are of special interest, and represent 
two distinct groups, the more important characters of which 
This section was especially designed to illustrate an Address by the writer, on 
The Introduction and Pema Pz of Vertebrate Life in America. This Journal, 
Vol. xiv, p. 337, Nov., 1877. 
¢ This Journal, yol. xv, p. 233, Sept., 1878. 
$ This Journal, vol. xv, p. 412, June, 1878. 
