Geological Papers. 69 



ing the mound is to be found. It is rarely that the lower John 

 Day is to be seen lying underneath the upper layers ; more com- 

 monly the area occupied by this formation is an exposed valley 

 whose floor is covered by ascending series of these mounds which 

 finally abut against the lava hills. 



The middle and upper John Day series resemble each other and 

 differ materially from the lower. They occur in steep cliffs of 

 ashy gray or bright green color, and weather into vertical columns 

 which rest upon harder layers,- usually of white or pink, that ex- 

 tend approximately horizontally through the face of the exposure. 

 The whole mass of material is cracked and seamed, and consists of 

 hardened nodules, between which is a softer matrix of the same 

 sort of material. When the irregular hardened masses are exposed 

 on all sides they slake off in concentric layers, which break down 

 and finally leave only scattered fragments of flint-like hardness. 

 These small pieces of hard substance lie upon all surfaces where 

 they can lodge and make the footing of one who climbs upon the 

 cliffs very uncertain. Such exposures occur only occasionally, and 

 there would seem to be no continuous formation over the whole 

 basin. Whether there ever was such a one is very uncertain, but 

 if this was the case then there must have been very extensive 

 weathering and erosion before the Tertiary lava flows buried the 

 region. 



The individual exposures of the middle and upper John Day 

 are from 100 to 500 feet high, and in the search for specimens it is 

 necessary to crawl over the surface of these almost vertical cliffs 

 and to look very carefully for bone fragments. Compared with 

 many other collecting grounds in the Miocene there are here com- 

 paratively few specimens, but by careful work we were able to find 

 enough to keep us busy most of the time. It is a very difficult 

 matter to remove the bones in good condition because of the lack 

 of homogeneity in the matrix. On digging into the cliff after a 

 specimen it will be found that for a part of the distance the bones 

 will lie in the hard nodules, and will then for a while extend 

 along in the seams that are filled with much softer material. For 

 this reason it is impossible to remove any large part of a skeleton 

 in one piece, and the individual bones have to be carefully re- 

 moved and pasted up in cloth. The bones themselves, however, 

 are in an excellent state of preservation and make beautiful speci- 

 mens. 



Most of the fossils in this region are mammalian, but in some 

 places turtles are numerous. The commoner specimens belong to 



