PLANT AND INSECT FOSSILS FROJNI THE GREEN RIVER 

 EOCENE OF COLORADO 



By T. D. A. COGKERELL 



Of the University of Colorado, Boulder 



The present paper continues the study of the Green River biota, 

 the fossils now described having been obtained by Mrs. Cockerel!, 

 John P. Byram, and the writer during the summer of 1922. The 

 oil shale region in Colorado is at the present time in a condition 

 extremely favorable to the paleontologist, owing to the great quan- 

 tities of shale thrown out from the yqty numerous assessment holes. 

 In a few years this material will decay, and it is probable that the 

 blasting out of fresh holes will be discontinued. The rock is very 

 hard and can not be readily worked with pick and shovel, as is done 

 at Florissant. We may therefore hope that means will be found in 

 the near future to send additional collectors into the region, to secure 

 the rich materials now readily obtainable. 



Since I last published on this subject Dr. F. H. Ivnowlton's ex- 

 cellent Revision of the Flora of the Green River Formation^ has 

 appeared. This puts our Imowledge of the flora, hitherto very im- 

 perfect and confused, on a good basis and makes further work rela- 

 tively easy. One previously published species has been omitted; 

 Firmianites aterrinius Cockerell - (Green River, Wyoming), 



The new materials now described indicate certain general con- 

 clusions- or results as follows : 



(1) The plants show that the flora is in many ways similar to 

 that of Florissant, with enough representative species to strongly 

 suggest that part of the Florissant flora is directly descended from 

 that of the Green River Epoch; while at the same time there has 

 been interval enough to change all or almost all the species. It is 

 probable that no Florissant species of flowering plant is actuailv 

 identical with any Green River species. 



(2) On the other hand, it is evident that part of the Floriss-ani 

 flora is derived from quite other sources ; also that the Green River 

 climate was warmer than that of Florissant. As we come to know 



• U. S. Geological Survey, Professional Paper 131-F. 

 2 Amer. Journ. Sci., November, 1909, p. 447, 



No. 2556.— Proceedings U. s. National Museum. Vol. 66. art. ig 



911S— 25 1 



