HAROLD’S DISCUSSIONS. 
U 
Geologists tell us that this break is very evident 
in Europe. In the British Isles everywhere the new 
rocks rest upon chalk strata, making it very easy to 
distinguish the new from the old. But in America 
there is so little evidence of erosion that it is almost 
impossible to know the new rocks from the chalk 
formations that preceded them. 
The break in the life forms, however, is marked 
in both continents. The old types of life were called 
upon to make way for their successors, and in most 
instances these were higher forms of life. Many of 
them were so well adapted to the new conditions that 
they still exist as types, though somewhat reduced in 
size. For this reason it is called the period of Recent 
Life, or by its Greek equivalent, the Cenozoic. 
On account of the fossils, particularly the shells, 
the lower part of the beds of the period is divided 
into three groups, known as the Tertiary (three¬ 
layered) strata. These consist of the Eocene (dawn- 
life), Miocene (middle-life), and Pliocene (more re¬ 
cent) layers, which together constitute what has been 
described as formation Aumber 6 (see page 47). 
Wherever the sea covered the land at the close of 
the Tertiary period, deposits, of course, continued. 
Some of these areas were elevated later, and became 
the dry land described as Humber 7, belonging to 
what geologists call the Quaternary (one of a set of 
four), or post-Tertiary, or Pleistocene. 
In different parts of Wyoming, rocks bearing quite 
different fossils are found lying upon those of the 
previous age. Bones of a number of animals have 
