214 GEOLOGY. ' 



connected them with tapirs and such generalized carnivores as 

 bears. Cdryphodon elephantopus was about the size of a small 

 elephant, but some of the species were much smaller than the mod- 

 ern tapir. 



Another group of animals described from these beds by Marsh, 

 were named Tillodontla. Like the preceding, they were highly 

 generalized in structure, and combined the hoofed toes of the Un- 

 gulata with the head of the bears and the incisor teeth of the ro- 

 dents. Thus far four clearly defined species have been described. 

 Among reptiles several species of crocodiles and many turtles have 

 been obtained. 



Green River Group. This group is unconformable to the pre- 

 ceding, indicating some changes of level preceding its deposition. 

 It overlaps the Vermillion group towards the west at least 200 

 miles (King). The sediments that constitute this group are 2,000 

 feet thick, and are exceedingly fine, indicating their deposition in 

 deep waters. In some localities, such as Barrel Springs, south and 

 east of Cathedral Bluff--, the shales of this group are extremely 

 carbonaceous, and are intercalated with fine, sandy members. 

 Many leaf impressions are found in them, and numerous fresh wa- 

 ter shells. 



Vegetable Remains of the Green River Group. Lesquereux has 

 described 82 species of plants from this group, but their general 

 facies is remarkably distinct from that of the preceding deposits. 

 Among these plants are six ferns, two species of Equisetae, eleven 

 conifers and nine grains and grasses (Glumaceoe). The willows 

 (Sallx) were represented by three species, the oaks (Quercus) by 

 five, hollies (Ilex) by four, sumac (Rhus) by two, and walnuts 

 (Juglans] by six species. Fig trees, the Cyprus, the giant cedars, 

 and the ash were still present, but the palms were gone. It con- 

 tains only a remnant of the Flora of the preceding group. Les- 

 quereux, in studying this Flora, came to the conclusion that it rep- 

 resented a vegetation characteristic of " high land, covered with 

 lakes, swamps, and deep forests of conifers with a thick under- 

 growth of ferns and shrubs." In the Tertiary it has its analogue 

 with the Flora of Oeningen in Switzerland, or upper stage of Eu- 

 ropean Miocene. As this vegetation is an upland flora, it is prob- 

 able that it does not so fully represent the vegetable forms that ob- 

 tained on the plains of Nebraska during this period as the preced- 

 ing Vermillion Group epoch. % 



