PEAUS.J RESUME — CENOZOIC ROCKS TERTIARY. 637 



difficult to identify the beds except by the color of their debris. Even 

 where there is a bluffy exposure the lines of stratification are hard to 

 follow. 



Organic contents. 



The materials entering into the formation of the group do not appear 

 to be favorable to the preservation of fossils. A few fragments of bones, 

 probably Umys, were obtained from the west side of Green Biver, above 

 Bitterroot Creek. Pebbles of the limestone included in the conglom- 

 erates of Station a near Bitterroot Creek yielded a few Carboniferous 

 forms. The fossils from Station 14 will be given under the Green Biver 

 Group, as they are probably from the base of that formation. 



GREEN RIVER GROUP. 



The change from the sediments I have included under the Wahsatch 

 Group to those I shall now take up is a marked one. Besting on the 

 soft variegated beds is a series of light-colored sandstones which are 

 followed above by calcareous layers and fissile shales. 



The area between Green Biver and the Big Sandy is covered with the 

 Green Biver Group until the northern portion of the basin is reached. 

 Xorth of the Xew Fork it is present only as cappings of the mesas that 

 stand between the streams. Along the east side of the Green, from 

 Xew Fork southward, the Green Biver shales and sandstones form 

 bluffs several hundred feet in height. On the west side of the river 

 above La Barge Creek the group is present only in isolated mesas. 

 South of that stream, however, it is the surface formation rising from 

 Green Biver to the westward and breaking off in bluffs that face Merid- 

 ian Ridge. Whenever seen, the group rests conformably on the Wah- 

 satch. It is seen dipping with the latter where it rises on Meridian 

 Bidge and in the Ham's Fork Plateau, but when upturned it appears to 

 have been very easily eroded, so that it generally ends in a bluff face 

 just east of the steeper inclination. This often makes it resemble an 

 unconformability ; but it is only apparent, for the Wahsatch beds are 

 always seen in position beneath the Green Biver Group, dipping in the 

 same direction and at the same angle. As we recede from the line of 

 greatest elevation the angle decreases, and that portion of the Green 

 Biver Group which was most inclined has been removed. 



In the Ham's Fork Plateau the group forms the surface of a shallow 

 synclinal which is so slight as to be scarcely noticed between Ham's 

 Fork and the mountain 'ridge to the westward. The beds here are 

 highly fossiliferous and contain, near the top, a layer of bituminous shale. 

 In the Bear Lake Plateau we have, just above the variegated beds, a white 

 sandstone which may represent a portion of the Green Biver Group, 

 but it is sou small that I have included it with the Wahsatch. At no 

 pomt in the district have we the peripheral portions of the group, so that 

 we cannot say whether or not there was any disturbance at the end of 

 the period. 



Organic contents. 



The Green Biver shales are highly fossiliferous, and had yieMed fossils 

 at several localities within the limits of our district previous to our ex- 

 plorations. In 1S73, Professor Cope found numerous remains of fishes 

 on Fontenelle Creek and on the east side of the Green, above the mouth of 

 La Barge Creek, and with them he found "insects and their larva;, shells 

 like Pupa and Oyrena, and millions of Cypris. The larva; are dipterous, 



