300 



H. F. OSBORN JURASSIC-CRETACEOUS TIME 



Morrison of hoth Upper 

 Jurassic and Lower Cre- 

 taceous Age 



J. B. Hatchei-, 1903, geol- 

 ogist and paleontologist. 



S. W. Williston," 1905, ge- 

 ologist and paleontolo- 

 gist. 



W. D. Matthew," geologist 

 and paleontologist. 



W. B. Scott, 1907. 



Chas. C. Mook, 1915, geol- 

 ogist. 



T. W. Stanton, 1909, geol- 

 ogist and paleontologist. 



T. W. Stanton, 1915. 



Morrison chiefly of Coman- 

 chian or Lower Creta- 

 ceous Age 



W. B. Scott, 1897, geol- 

 ogist and paleontologist. 



S. F. Emmons, 1890, geol- 

 ogist. 



Logan, 1900, geologist. 



N. H. Darton, 1915, geol- 

 ogist. 



W. T. Lee, 1915, geologist. 



E. W. Berry, 1915, pale- 

 obotanist and geologist. 



Morrison of Upper Jurassic 

 Age 



C. A. White, 1883, inver- 

 tebrate paleontologist. 



Edw. D. Cope, 1884, pale- 

 ontologist. 



Henry F. Osborn, ISSS, 

 paleontologist. 



Lester F. Ward, 1900, pale- 

 obotanist. 



Wilbur Knight, 1900, geol- 

 ogist. 



E. S. Riggs, 1901, paleon- 

 tologist. 



O. C. Marsh, 1896, paleon- 

 tologist. 



F. B. Loomis, 1901, pale- 

 ontologist. 



C. W. Gilmore, 1909, pale- 

 ontologist. 



W. J. Holland, 1912, pale- 

 ontologist. 



H. E. Gregory, 1914, geol- 

 ogist. 



Character of paleontologic Evidence 



The fact that the evidence from paleontology has thus far not been 

 found conclusive is largely due, as stated above, to lack of thoroughness 

 in the comparison both of the carnivorous and of the large herljivorous 

 dinosaurs of the Morrison, which include forms resembling those which 

 range from the Oxfordian through the Kimeridgian into the Purbeckian 

 and even into the Wealden. In general, it is said the Morrison dinosaurs 

 are more specialized than those which have been found in the true British 

 Jurassic formations, but there are some very striking exceptions. The 

 mammals appear to be closely related in their stage of evolution with 

 those of the Purbeckian of England. This would tend to correlate at 

 least some parts of the Morrison witli the Purljeckian of England as 

 Upper Jurassic. This was the main strength of Professor Marsh's argu- 

 ment. The invertebrate fauna gives little satisfactory evidence as to 

 age. The Morrison flora is scanty, consisting almost entirely of cycads. 

 Lester F. AVard considered the cycads as proof of Jurassic age ; but some- 



- W. B. Scott : "An Introduction to Geology." 8vo. Macmillans, 1907, pp. 680-681. 

 "It has been suggested by Professor Williston that different areas of the Morrison are 

 of different dates, just as we saw that the Millstone Grit (Upper Carboniferous) of the 

 Mississippi Valley is not a single uniform bed, but different beds of similar character, 

 formed successively and corresponding to several horizons in the great mass of the 

 Appalachian Pottsville. On this view, which is probably the solution of the problem, 

 the Morrison includes several distinct horizons, extending from the Upper Jurassic into 

 the Lower Cretaceous, but the discrimination of these horizons is yet to be made." 



• Personal communication, 1915. 



