nirer ]'iillejis of fix- Ozark- I'hilcdu. — Jl crshcn . 8;-19 
eroded plain is not confined to regions underlain by any one 
formation, but passes alike over Cambrian, Silurian, and Car- 
boniferous strata : nor is it confined to the Ozark plateau, but 
descends by a gentle slope to the level of the upland country 
which surrounds the plateau on all sides, excepting the south- 
east. Thence it extends across the prairies, joining the 
similarly channeled plains of other uplifted tracts in the 
eastern portion of the continent; and westward it passes 
across the Coal Measures until it sinks under the Cretaceous 
strata of the Great plains. It is the Jura-Cretaceous pene- 
plain, which was produced by subaerial erosion during a long 
period approximatel}^ coinciding with the Mesozoic ei-a. At 
or near the close of Cretaceous time the Ozarks did not exist, 
either as a plateaii or mountains, but their present site was 
occupied by a low, marshy plain of very slight relief, jirob- 
ably nearly- at sea level. 
But there are, at widely separated intervals in the Ozark 
region, small hills and short ridges, which rise from twenty- 
live to fifty or perhaps occasionally one hundred feet above 
the level of the peneplain. They are generallj^ composed of 
sandstone, and in the western part of the region are fre- 
quently largely made up of coarse conglomerate which belongs 
to the basal member of the Coal Measures. When of some 
material which powerfully resists erosion, they are steep- 
sided and quite prominent, affording extensive views over the 
surrounding country. These inounds and small ridges gener- 
ally occur on the watershed between the principal streams, 
but are also found far within the broken country, often stand- 
ing on the edges of the deepest valleys. 
The examples of these ridges and knobs which 1 have ex- 
amined particular!}^ are on the watershed between the Osage 
and Missouri rivers, on the crest or general watershed of the 
plateau between Lebanon and the Arkansas line, in the broken 
country of Barr}^ and Stone counties, and beyond the Ozark 
uplift in western Missouri and southeastern Kansas. But from 
maps and other sources I learn that they are widely scattered 
over the Ozarks in bf)th Missouri and Arkansas, Belonging 
to the same class are doubtless the ^•nutunds" in Bates, Cass, 
Johnson, Lafayette, and other counties rti' western Missouri, 
described by Broadhcati as "ridges several miles long, and oc- 
