PEALE.] EESUME CENOZOIC EOCKS— TERTIAEY. 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 Eiver, 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 Eiver 

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



aEEEN 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. Eesting 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 Eiver and the Big Sandy is covered with the 

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

 ISTorth of the ISTew Fork it is present only as cappings of the mesas that 

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

 l^ew Fork southward, the Green Eiver 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 Eiver to the westward and breaking off' in bluffs that face Merid- 

 ian Eidge. Whenever seen, the grouj) rests conformably on the Wah- 

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

 Eidge and in the Ham's Fork Plateau, but when uj)turned it appears to 

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

 just east 6f the steeper inclination. This often makes it resemble an 

 uncouformability ; but it is only a])parent, for the Wahsatch beds are 

 alwa5^s seen in i^osition beneath the Green Eiver Group, dij)ping in the 

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

 greatest elevation the angle decreases, and that x)ortion of the Green 

 Eiver Group which was most inclined has been removed. 



In the Ham's Fork Plateau the grouj) 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 tlie Bear Lake Plateau we have, just above the variegated beds, a white 

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

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

 poijit in the district have we the i)eripheral portions of the group, so that 

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

 the i)eriod. 



Organic contentsi^ 



The Green Eiver shales are highly fossiliferous, and had 3' ielded fossils 

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

 plorations. In 1873, 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 foimd "insects and their larvre, shells 

 like Fu])a and Oyrena, and millions of Oypris. The larvie are dipterous, 



